set value to 0 if series data doesn't have that key, as column charts can't have nulls
set value to 0 if series data doesn't have that key, as column charts can't have nulls
Merge pull request #22 from ygelfand/master

highcharts doesn't like null values in data for column series, results in 'x is undefined'
Fixed issue w/ library option - closes #23
Merge branch 'master' of https://github.com/ankane/chartkick
Upgraded to chartkick.js 1.1.0
Version bump
Updated readme
Better example
Merge