Work in progress refactoring ClickResolver.js to Ray.js

* Added `camera_orthographic` example.

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

* 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

Added rudimentary 3x3 matrix class (just transpose, as this is needed for normal matrix).

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

  * Added getCenter to Face4

- Minor tweaks

 * Bug Fix: Matrix4.makeInvert was calling a non existent scale method. Replaced with multiplyScalar.
 * Bug Fix: DirectionalLight wasn't normalizing the direction vector.
 * Added lights to the scene for test.html

* Additional `Matrix4` and `Vector3` methods

* `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.

- 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.

- Fixed overdraw when using stroke materials

* Removed SVG rgba() workaround for WebKit. (WebKit now supports it);

- CanvasRenderer supports TextureUVMappingMaterial.
- Moved UVs to Geometry.
- Minor clean up

+ Workaround for WebKit not supporting rgba() in SVG yet
+ Aesthetic changes on the readme file

CanvasRenderer: Min of ClearRect with ClipRect