Add repo compare API
add blob content API
remove useless check for available hook events

fixes #83
ability to update hook triggers
Merge branch 'zlx-feature/two_repository_api'

Conflicts:
	lib/gitlab/client/repositories.rb
	spec/gitlab/client/repositories_spec.rb
Revert "add blob content API"

This reverts commit 9cccac6f4586cfca666f4727b52b945c1ef1577d.
fix docs and specs
release v3.3.0
add more badges to README.md
Refactor of Gitlab::Shell to hopefully make it more readable & testable.  Wrote tests for some Gitlab::Shell & Gitlab::CLI::Helper methods.  Other minor improvements and refactors.