Move translations outside repo

See https://github.com/roots/roots-translations
LiveReload - reference non-minifed assets
Swap input/label on searchform
Re-add excerpt and wp_title functions from cleanup.php

Rename custom.php to extras.php
Add comments about GA
Add grunt-autoprefixer
Add time-grunt
Use apply_filters for main and sidebar classes
Use 'roots/' for filters
Use sr-only class on searchform, move label again because of input-group styles
Update watch tasks
Update README
Use grunt-wp-assets
Offer just one header, the BS top navbar