Add method to delete branches

I have not quite made the spec run correctly
Fix doc. Use delete_ref for delete_branch
Re-write spec to use api-playground/api-sandbox
Implement Feeds API #feeds method.
Correct parameter for updating label name is :name.
Add .update_branch method
Merge pull request #375 from barisbalic/update-labels-documentation

Correct parameter for updating label name is :name.
change test to check login variable instead of hardcoded value
Merge branch 'delete-branch'
Merge pull request #376 from joeyw/fix-gist-spec

change test to check login variable instead of hardcoded value
add feed method to get specific feed, middleware to parse feeds
Add collaborator? method to client
Merge pull request #379 from md5/check-user-collaborator

Add collaborator? method to client
Merge pull request #374 from joeyw/implement-feeds-api

Implement Feeds API #feeds method.
Modify paginate to take a block for custom concatination of the requests.
Add custom concatination block to Search#search

The search api wraps the results in a layer, this change provides a block to
the paginate method to custom combine the results.
Merge pull request #382 from joeyw/fix-search-pagination

Fix search auto pagination
List org public members

Refs #373
Fix method name in spec description
Fix typo in docs