`Rubocop` is now `RuboCop`

See https://github.com/bbatsov/rubocop/commit/ff167d8f202baf7a68955db0aaf0dc29afb7e7ee
Merge pull request #1295 from nevir/patch-1

`Rubocop` is now `RuboCop`
Add <head> to 404 so Livereload can add its script to the page
Add a protective require
Make option documentation consistent.
Test gzip extensions option.
Accept list of paths to exclude from gzipping.
Merge pull request #1268 from AndrewKvalheim/gzip-ignore

Excluding paths from gzipping
Merge branch 'v3-stable'

Conflicts:
	middleman-core/lib/middleman-more/extensions/asset_hash.rb