Add sync command to be able to commit/pull/push at once
Add commands to pull and push only
PEP8
Merge remote-tracking branch 'upstream/develop' into git_sync

Conflicts:
	pytex/commands/versioning.py
	pytex/versioning/git.py
No need to add before push and pull
Merge pull request #13 from wichtounet/git_sync

Commands to push/pull/sync the Git repository
Merge remote-tracking branch 'upstream/develop' into rst_processor_clean