Allow datum index to be passed as a third parameter to the data labels format function
add support for array of tick label strings #139

formatted tick label can be an array of strings, each will be displayed
in a line
Fix mouse event for multiple xs - #663
Support unicode in class names - #665
Fix point.show when redraw - #666 #681
Use 0 as default for axis.x.tick.rotate
Stop interval when destory() called - #668
Support multiline tick text on normal x axis and introduce axis.x.tick.multiline option - #139 #670
Fix legend background for inset - #326
Fix conflict
Merge branch 'edcartre-master'
Fix conflict and add spec
Merge branch 'dungsaga-master'
Merge pull request #1 from masayuki0812/master

Update
Added a 4th param to data label format callback

This gives us more control of data labels. Now we have access to: value,
id, i (index of each datum inside a series), j (index of each series).
Avoid recomputing client rect for showTooltip - #637
Avoid binding 3rd party property to c3 API - #647
Use axis.y.tick.values for y grids if it's set - #680
Fix culling when y tick values set
Fix x axis clip height