Merge tag '2.6.2' into develop

House keeping
Merge tag '2.6.3' into develop

2.6.3
Merge tag '2.6.4' into develop

Boxsizing file is missing contents
Update content main function to use <main> element. Update Modernzir. Closes #229
Adds jQuery CDN jQuery as pref source. Closes #253
Add filename based cache busting via GruntJS. Closes #250
Remove legacy JS min files
Create "build" task for static assets. To be run before deploying a release.
Add pngquant to imagemin task. Add imagemin task to build task.
Update package versions. Compress images
Finalise comments on build task. Closes #252
Avoid JShint running on minified files
Remove unwanted map directory. Closes #254
Doc Version
Merge branch 'release/2.7.0'