A lot of things going on in this commit:

- added tangents computation for geometries
    - mesh must have UV coordinates
    - to be called explicitly once geometry is loaded like this: geometry.computeTangents()
    - tangents are stored in Vertex objects
    - quads are not solved properly (though workaround hack seems to work at least somehow, as far as each vertex appears at least somewhere)

- extended VBOs in WebGLRenderer to include tangent streams (when available)

- added "normal" shader to ShaderUtils (to be used with MeshShaderMaterial)
   - Blinn-Phong with one directional and one point light (7 varyings gone, just one spare)
   - normal maps are in tangent space
   - displacement maps use simple luminance value (could be changed if better precision is needed)

- displacement mapping uses vertex texture fetch
    - this requires GPU with Shader Model 3.0
    - not currently supported in ANGLE
    - for this, added "supportsVertexTextures" method to WebGLRenderer API, so that application can handle this

Maybe `Geometry::computeNormals` should be renamed to `Geometry::computeFaceNormals`?

Added irc channel info in README.

Matrix4.transformVector4 ⟶ Matrix4.multiplyVector4

The most tangible practical effect is that demos with multiple Lucys / Walts are now initialized much faster ;).

Reuse is achieved mostly by moving mesh chunks / VBOs (formerly called materialFaceGroups) from Mesh into Geometry.

This means sorting of geometry by face materials + breaking large geometries into chunks now has to be done after construction of geometry.

It becomes a step in the usual sequence:

    geometry.computeNormals();
    geometry.computeCentroids();
    geometry.sortFacesByMaterial();

If geometry is constructed programmatically (e.g. with GeometryUtils.merge), this has to be called afterwards.

Also of note: single geometry cannot be reused both for flat and smooth shading, as only one stream of normals is baked into VBO.

CanvasRenderer/SVGRenderer: RenderableFace4 is now gone. Unfortunately it created more problems than it solved.
CanvasRenderer now with ShadingSmooth, or something along the lines...

* 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 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

* `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

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

- 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

Vector3.cross -> crossSelf
added Vector3.multiplySelf and others (kile)

Added THREE namespace
Camera.x -> Camera.position.x
Camera.target.x -> Camera.target.position.x
ColorMaterial -> ColorFillMaterial
FaceColorMaterial -> FaceColorFillMaterial
Materials are now multipass (use array)
Added ColorStrokeMaterial and FaceColorStrokeMaterial
geometry.faces.a are now indexes instead of links