Removed IndexBufferAttribute. Promoted index attribute to BufferGeometry. Maybe .addIndices() instead?
/ping @benaadams

The example web page now allows the change of different properties of
the circle's texture:
- wrapS
- wrapT
- offset
- repeat

The change on the js files are only formatting ones (mrdoobapproves)

Add a new variable to avoid instantiation of a Vector3 in each call to
THREE.Triangle.barycoordFromPoint().

Defer calculus after the near plane / far plane test. Need to do a copy
of intersectionPoint due to the applyMatrix4.

Test with a PlaneBufferGeometry and a BoxGeometry. Didn’t test with
indexed BufferGeometry (don’t have any in my program) but I’m quite
comfortable the uvA, uvB and uvC are the right one in that case.

Mesh.js raycast method is updated to calculate intersection point in uv
coordinates. The calculus is done in the new inner method
textureIntersection and added to the object returned as the uv property.

Texture.js has a new public method, transformUv, that convert the
coordinates from uv (range 0 to 1) to the real texture coordinates. The
input parameter is modified on output. Useful to have the intersection
point in texture coordinates.

There is no example in this commit because I only have example with
canvas, no with plain image.

- Better inheriting of `clone` + `copy` methods where appropriate. This is done by calling `new this.constructor()` in parent classes. `this.constructor` refers to the current instance's constructor, so it should all compose nicely;

- Pass in attributes directly as arguments to constructor when cloning, where appropriate (if arguments pattern is different from parent class). This mean `copy` isn't relied on to set those attributes.

- Change order of `clone` in some files (for better visibility into its relationship with `copy`, and to maintain consistency; can return to previous order if necessary);

- Fix CubeTexture's clone method

Array overflow made raycasting on indexless BufferGeometry horribly slow (for one it was doing 3 times more work, but more importantly, array access outside of array bounds are horribly slow)

Store reading and writing to `.offsets`.

Avoid mutations to `.drawcalls` from outside the `BufferGeometry`.