* Minor fixes (Geometry normal calculation)
* Isolated Matrix3 code into `Matrix3.js`
* README and TODO updated

In Chrome it looks more or less ok, but it has some problem in Firefox 4 (with some camera angles there are black areas around edges).

Also updated Python builder scripts and examples to include this new material.

* MeshBitmapUVMappingMaterial -> MeshBitmapMaterial. Second param is mode, which is THREE.MeshBitmapMaterialMode.UVMAPPING by default.
* Removed MeshFaceColorFillMaterial and MeshFaceColorStrokeMaterial
* Added MeshFaceMaterial ( it uses the face.material for that pass )
* CanvasRenderer and SVGRenderer per face material logic changed.
* SVGRenderer supports particles again.
* WebGLRenderer currently broken :/
* Code clean up

Refactored multimaterials to also work with non-textured models composed from multiple material groups.

Old version was doing massive overdraw (whole mesh was drawn for each material).

Even current solution is still quite messy: there is a different behavior for stroke and fill materials (when used as secondary materials).

Stroke materials are applied to the complete mesh (as most common use case seems to be wireframe) while fill materials now apply only to faces within single material group (when "decalIndex" property of secondary fill material is set).

Extended CanvasRenderer to be able to handle decals (MeshBitmapUVMappingMaterials as secondary materials).

For decals you need to set "decalIndex" property of the material (corresponding to materials index of the original mesh UV material).

Added multimaterials example.

Fixed forgotten sphere smoothing in OBJ converter example.

Added OBJ converter test example.

Modified Three.js to handle converted models:

 - extended WebGL renderer to use texturing
   - broke down model into multiple VBOs according to materials
   - textures are lazy created when images get loaded
     (converter takes care of resizing images to nearest power of 2
      dimensions using 2d canvas)

 - changed material array semantics in Mesh object
    - before: multiple materials were applied to all faces (broken in WebGL, needs multitexturing shader)
    - now: there is only single material per face, but one mesh can have faces with different materials

 - added per vertex normals (to get smooth shading in WebGL)

* `CanvasRenderer` and `SVGRenderer` basic lighting support (`*ColorStroke`/`*ColorFill` only)
* `Renderer` > `Projector`. `CanvasRenderer`, `SVGRenderer` and `DOMRenderer` do not extend anymore
* Interactivity base code (hdi folder). To be refactored... ([mindlapse](http://github.com/mindlapse))
* Added `computeCentroids` method to `Geometry`
* Included `Stats.js` directly in the `/examples` folder to avoid the need of internet for playing around

- Minor tweaks

* Additional `Matrix4` and `Vector3` methods

- Camelcased the minified files (it feels weird both ways anyway...)

- Face4 with MeshBitmapMaterial gap fixed

- `three_debug.js` checks for broken UVs and display these faces with pink color instead

* `Face4` now supports `MeshBitmapUVMappingMaterial`
* Changed order of `*StrokeMaterial` parameters. Now it's `color`, `opacity`, `lineWidth`.
* `BitmapUVMappingMaterial` > `MeshBitmapUVMappingMaterial`
* `ColorFillMaterial` > `MeshColorFillMaterial`
* `ColorStrokeMaterial` > `MeshColorStrokeMaterial`
* `FaceColorFillMaterial` > `MeshFaceColorFillMaterial`
* `FaceColorStrokeMaterial` > `MeshFaceColorStrokeMaterial`
* `ColorStrokeMaterial` > `LineColorMaterial`
* `Rectangle.instersects` returned false with rectangles with 0px witdh or height

Old Vector and Matrix constructor functions would create all methods and
make assignments with each call. A lot of speed-ups can be made by using
shared properties through the prototype chain. Since methods and
initialized properties are shared among all instances they're only
created once.

Some tests can be seen at examples/performance-test.html

Some results:

    Chrome

    //6.4 times faster
    performance-test.html:25 Vector2 x 5000000: 213ms
    performance-test.html:30 Vector2Orig x 5000000: 1366ms

    //8.3 times faster
    performance-test.html:37 Vector3 x 5000000: 241ms
    performance-test.html:42 Vector3Orig x 5000000: 2015ms

    //3.8 times faster
    performance-test.html:49 Vector4 x 5000000: 278ms
    performance-test.html:54 Vector4Orig x 5000000: 1059ms

    //7.5 times faster
    performance-test.html:61 Matrix4 x 5000000: 937ms
    performance-test.html:66 Matrix4Orig x 5000000: 7004ms

    Firefox

    //6.8 times faster
    Vector2 x 50000: 45ms
    Vector2Orig x 50000: 307ms

    //11.5 times faster
    Vector3 x 50000: 48ms
    Vector3Orig x 50000: 550ms

    //3.8 times faster
    Vector4 x 50000: 61ms
    Vector4Orig x 50000: 234ms

    //9.4 times faster
    Matrix4 x 50000: 199ms
    Matrix4Orig x 50000: 1878ms

where "Orig" are old versions of the objects.

Running these tests multiple times can yeild different results due to
browser cache. However the results are always kind of similar in terms
of speedup.

* `Particle` now use `ParticleCircleMaterial` instead of `ColorFillMaterial`
* `Particle.size` > `Particle.scale.x` and `Particle.scale.y`
* `SVGRenderer` currently out of sync

- Matrix4.lookAt fix (CanvasRenderer and SVGRenderer now handle the -Y)
- Color class now using 0-1 floats instead of 0-255 integers

- Enabled Scene.removeObject
- Removed computeNormals() from Geometry

- Simplified lookAt in Matrix4
- Added cross() in Vector3

- Object3D.overdraw = true to enable CanvasRenderer screen space point expansion hack.