use XMLHTTPRequest2 if available to fix IE11 errors with overrideMimeType
added support for parsing ArrayBuffer from XHR2 response
changed readByte() and readString() to read from Uint8Array returned by xhr2
replaced use of overrideMimeType xhr request with xhr2 request
fixed snaping
Merge branch 'ie11-ctmloader-xhr2' of https://github.com/MSOpenTech/three.js into dev