Unit tests for ansible.utils
Fix docs for ec2_lc module.
Update CODING_GUIDELINES.md
Add integration test for apt_repository

Tests several ways to specify the repository.  For every repo added, the test
asserts that:

 * the apt-cache was updated as expected (depends on `update_cache` parameter)
 * the PPA key was installed (depends on `repo` format)
Merge branch 'unit-tests' of https://github.com/sivel/ansible into sivel-unit-tests
Add guide for Google Cloud Engine.
Add GCE guide and retool a bit to show the add_host interactions, improvements/upgrades are welcome.

Had to shoot the recently merged nova_group module in the head temporarily as it contained a dict comprehension, which means it can't work on all the platforms
and was also breaking docs builds on CentOS.  Will engage with list about that shortly.
Merge branch 'sivel-unit-tests' into devel