refactored groups pagination
next link corrected
groups paginate works
removed get_new_paginate_query_args and tests
get_*_links tests and docs added
self link not included while listing groups

Since the same has been requested anyways. Made changes to
`get_collection_links` to not give self link if rel is None
Handling collection > limit size

Giving marker based on limit value
Merge pull request #415 from rackerlabs/refactor_pagination_groups

Refactor groups pagination