Merge branch 'dev'

Merge branch 'v2.1.0'

Merge branch 'v2.0.0'

Merge branch 'dev'

Restore proper text alignment in grid items that use centred grids

Ensure centred grids properly extend regular ones

Add grid centring class

DRY out relative positioning used on silent push and pull

Merge branch 'dev'

Add `!default` flag to vars.

Fixes csswizardry#10