Ignore `.themes` folder in Sublime

Makes for easier searching, as only the `source` folder files should
be modified
Take advantage of Inuit’s nice vendor mixin
Set title for homepage to just be the site title
Initial homepage hero “welcome” copy
Update hero background to be office photo
Add Guard for auto-reloading dev sites

Requires the LiveReload browser extension, but makes for faster dev!
Update the README to reflect ET's usage
Use American English spelling of license
Update homepage grid copy w/ 3 areas of concern
Initial addition of dev avatars using Gravatar