Annotation support (#1220)

See travis-ci/travis-ci#1220 for more info

Add annotations to the UI

## TODO

- [x] Get the `hasMany` relationship to work
- [x] Show the annotations on the job page
- [x] Show the annotations on the build page for single-job builds
- [x] Work with pusher messages (link updating)
- [x] Extract AnnotationsView
- [x] Replace provider name with image if one is given