Curies, embeds, zoom and more

big commit, getting various functionality playing nice together:

* define curies in base representer
* define self in base representer
* add profiles to all self links
* add `embed` and `embeds` methods to representer related resources, control default zoom
* add to models and base controller to tag instances if they are the root resource, (and get curies and embeds)
* add in support for `zoom` (or `z`) request param to show more embeds in root resource

some smaller fixes:
* new relic added for basic request analysis
* return 404 for AR not found errors
* rename `PRXModel` to `BaseModel` to be more consistent
* make `PagedCollection` have smarter defaults, not need a http request obj to construct
* use `title` attr in links rather than sometimes `name` and sometimes `title`