Add info on where to get 3.0 unstable files

Also added note that 3.0 is not production-ready.

[skip ci]
Remove reference to angular 1.2.4
Submit code coverage report to coveralls.io
Add coverage config to serialsauce tasks
Try to fix coverage reporting
Add coveralls.io badge to README

[skip ci]
Fix for #1352.  cell contents needed to be sized 100% height and width
Fixed issues with cell editing
Merge pull request #1356 from lukasspee/3.0-cell-editing

Fixed issues with cell editing