[CHEF-955] Turned on remote tracking branch setup for 'origin' remote in git provider
[CHEF-955] Refactored remote tracking setup tests into a separate context
[CHEF-955] Changed behavior of setup_remote_tracking_branches method

Refactored the method to use appropriate git command depending
on the current status of git config.
[CHEF-955] Added condition running remote set-url only when neccessary
[CHEF-955] Added tests to document the current state of add_remote method
[CHEF-955] Refactored add_remotes function to use setup remote tracking branches
[CHEF-955] Updated remote branch url change command

Using 'git config' instead of 'git remote --set-url' to assure
compatibility with git < 1.7.0
[CHEF-955] Test refactoring and formatting cleanup

Organized the remote branches setup tests into describe blocks.
Removed some trailing spaces.
[CHEF-955] Made setup_remote_tracking_branches parameters to be required

Removed uncessary complexity with checking for presence of both
parameters for setup_remote_tracking_branches.
[CHEF-955] Test fixes after rebasing the branch

Removed uneeded 'converge' commands and some log_level param assumptions from spec