Editor: changed exports to use "text/plain" MIME type.

This make Firefox behave consistently with Chrome - on clicking export buttons content is opened in a new tab instead of triggering "save" modal dialog.

See discussion: https://github.com/mrdoob/three.js/commit/dc71940a851caa4abf5176421d413d46f1abf3f5
Changed scene format / SceneLoader so that lights can be a part of scene graph.

Lights now live in "objects" section together with meshes instead of its own "lights" section.

TODO: cameras should also follow this pattern.
Changed scene format / SceneLoader so that cameras can be a part of scene graph.

The same like for lights, cameras now live in general "objects" section.
Merge remote-tracking branch 'alteredq/dev' into dev
Merge remote-tracking branch 'mdeck/dev' into dev
Added support for vertex normals to Ribbons.

Not tested yet, but it should work in the same way like vertex colors in Ribbons: add one Vector3 with normal per vertex to "geometry.normals" array.

It's then up to the application layer to fill in proper values. It's use case specific how normals for triangle strips would get computed - for simple ribbon meshes it could be very similar like smooth normal computation for regular Mesh objects.

If degenerate triangles are used for pseudo-connected single ribbon mesh planes, application would need to take into account vertex adjacency.
Editor: added cameras and lights to scene export.
Editor: added keeping track of geometries loaded via loaders to scene export.

This is going to be tricky for models loaded as full scenes like Collada or OBJ (though there first we will need to figure out how to handle these at all in scene format / SceneLoader).
Editor: refactored scene exporter to handle properly hierarchies.
Update docs/api/extras/geometries/CylinderGeometry.html
Fixed BufferGeometry getting id = NaN.
Merging master branch.
Merge branch 'master' into dev
Updated builds.
Merge remote-tracking branch 'jpryne/patch-2' into dev
object.clone() now (recursively) handles children too.
Hopefully easier to understand offset array creation code.
Added support for fog to Sprites.

Just set "sprite.fog = true" to get scene fog working on the sprite.

Internally, implementation is a bit different than for other objects: because there is just a single material for all Sprites, fog is always compiled into the shader and it's turned on/off (or fog type is changed) via uniform.
Added missing custom attributes buffers deallocation for Lines and ParticleSystems.
Added custom attributes support for Ribbons and corresponding example.

See #1985