v0.9.0: line wrapping & image diff bounding boxes

Changes:

• Long lines now wrap instead of scrolling horizontally. (codediff update)
• Only 10+ common lines will be elided (no more "Show 2 more lines"). (codediff update)
• Show bounding boxes for the changed region in image diffs (via ResembleJS)
• Updated to React 0.12 and react-router 0.11