docs(guide/$location): replace host.com addresses with example.com

The host.com links on this documentation page took you to an ad page of dubious content.
Now changed to example.com, in accordance with RFC 2606

Closes #4206
docs(ngClass): clarify the description

Closes #4220
docs(ngInclude): clarity, formatting

Closes #4222
Merge branch 'master' of https://github.com/angular/angular.js
componentizd!