Content attribute

Switch breakpoint name from data attribute to content attribute.
Merge pull request #8 from geelen/master

Add the breakpoint class to HTML before DOMready
Merge pull request #9 from jonathantneal/master

Switch breakpoint name from data attribute to content attribute.
Added missing semicolon. (jshint)
Updated grunt to 0.4.0
+ Grunt plugins
Updated grunt environment to use jshint, uglify.
Added a .gitignore
Added grunt dep.
Updated travis yaml to install grunt cli
Update node for travis