v2.3.0

@driusan

General changes
- Travis continuous integration set up for repo. (@driusan)
- Browser capability checks now stored as constants. (@tsherif)
- Documentation updates. (@tsherif, @natacha-beck)
Surface Viewer
- Bundled three.js version updated to r69. (@tsherif)
- Use indexed geometry if extension OES_element_index_uint is supported. (@tsherif)
- Pass data to and from web workers as transferable objects. (@tsherif)
- Fixed Wavefront OBJ parsing. (@tsherif)
- Renamed mniobj intensity data format to text intensity data. (@tsherif)
Volume Viewer
- Simplified volume object model. (@tsherif)
- Fixed bug in zooming. (@tsherif)
- Renamed volume.min and volume.max to volume.intensity_min and volume.intensity_max. (@tsherif)

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