Include response headers in RequestErrorEvent.
Move @private to the end of the jsdoc
Fix test failures caused by incomplete stubbing of XMLHttpRequest.
Update CHANGES.md.
Add missing file
Update CHANGES.md
Update comments
Merge pull request #1455 from AnalyticalGraphicsInc/responseHeaders

Include response headers in RequestErrorEvent.
Merge master to gltf
Fix models after merge
Merge branch 'gltf' into gltf-wtf