changed location of images fixes #71
minor
fixed #67, and moved zero line styling to the css
fixes #75 one too many y-axis tick groups
Merge branch 'master' of https://github.com/Quartz/Chartbuilder
Merge branch 'master' into gh-pages
Merge branch 'gh-pages' of https://github.com/Quartz/Chartbuilder into gh-pages