Adding back stack percentage for histogram

Conflicts:
	panels/histogram/module.js
Merge remote-tracking branch 'selvakn/master' into stackPercent
Cleaned up the Grunt config a bit, removed an unneeded dep
Merge pull request #514 from spenceralger/gruntfile-cleanup

Cleaned up the Grunt config a bit, removed an unneeded dep
Readded percent stacking, fixed bug when area = 0, added view options to histogram outside of editor
Merge branch 'stackPercent'
Switched to grunt-contrib-compress, added tar.gz archive
Adjusted margins
Fix for #355
Make panel extra icons more obvious, fix overlap, add tooltips, add method for panels to define custom modals
improve panel extra icon hover
removed redundant divs
Added interval selector to histogram
Added interval options to panel
better-looking histogram checkboxes
fixed the path to the leaflet image directory
Merge pull request #518 from spenceralger/gruntfile-cleanup

fix the path to the leaflet image directory
Added explicit path to leaflet markers
switched up the build process a bit more, so most of the build occurs in-place, meaning the src and dest options are the same. This allows us to simple copy everthing at once and not need to specify all the edge cases like I did previously in copy:everything_left_in_src
'Add panel' hinting in empty spaces