Changes all paginated endpoints to return proxies

Rather than fetching the first page of objects
a proxy is returned and the user can use the
proxy to fetch the records they need.
Removes #total_count
Adds better HTTP error handling
Renames #all to #fetch
Moves valid search parameters to the right class
Cleans up requires

Changes to use require_relative. Deprecates 1.8.7 
support.
Refactors search methods to re-use the logic
Adds support for fetching clips by URL or created after time
Removes unnecessary line of code from test

It was never run if the test was passing.
Moves test helpers to separate files
Removes Ruby 1.8.7 monkeypatch
Adds 1.8.7 deprecation notice to changelog
Pick
Adds ReadCollectionResource module

It is used by resources that are used only for
reading, not for saving or destroying.
Unifies follower and following tests
Fixes the liking

Previously the liking was a bit all over the place.
Now fetching likes will always return proxies,
liking a clip is done from a clear place (Clip)
and everything is tested.
Changes the argument order for resources

Maybe going to named arguments would make sense.
Adds more tests for Clip & FollowRelationship