Show values on bar chart

This patch shows values on each bar by appending text nodes to bars. Values will appear if global variable showValues is true. For better control it should be made a config option.

Second change is about shouldShowTickText function. It returns always true, because when using axis:x:categories, I wish all axis values to appear.
Added style for the bar values patch

Added style for the bartxt class for bar values in the c3.js patch.
Add axis.x.tick.culling and axis.x.tick.count option and fix jshint - #45
Show formatted value in bar text - #45
Fix show value on chart - #45
Merge branch 'master' of https://github.com/fiery-/c3 into fiery--master
Fix css for text on chart - #46
Fix value on chart with line chart
Remove unnecessary axis call
Refactor draw bar and text
Fix bar width when categorized axis
Fix c3.min.js