Fix collada loader when examples are viewed through server.

[tapio]

The following examples where broken on mrdoob.github.com and when
viewed through a local python web server. file:// worked.

http://mrdoob.github.com/three.js/examples/webgl_loader_collada.html
http://mrdoob.github.com/three.js/examples/webgl_loader_collada_keyframe.html
http://mrdoob.github.com/three.js/examples/webgl_loader_json_blender.html

Reason was request.responseXML being null for some reason in the ColladaLoader. First I tried adding request.setRequestHeader('Content-Type', 'application/xml');, but that didn't help, so I resorted to parsing the request.responseText, which contained the payload.

Tested on Firefox and Chrome (both failed first, now fine).

Note: webgl_loader_json_blender.html also complains about the following on http://mrdoob.github.com/three.js/examples/webgl_loader_json_blender.html, so this might not be enough to fix that one on the server (local and python server work though, so probably missing the src-folder?).

GET http://mrdoob.github.com/three.js/src/loaders/GeometryLoader.js 404 (Not Found) webgl_loader_json_blender.html:35
GET http://mrdoob.github.com/three.js/src/loaders/LoadingMonitor.js 404 (Not Found) webgl_loader_json_blender.html:35

[mrdoob]

Good catch!
Cherry picked the patch on the master branch and merged into the dev branch.

Thanks!

Note: webgl_loader_json_blender.html also complains about the following on http://mrdoob.github.com/three.js/examples/webgl_loader_json_blender.html, so this might not be enough to fix that one on the server (local and python server work though, so probably missing the src-folder?).

Oh man... that's pretty sloppy of me. That's been broken since r50. These files are a wip new loading system... :S