TEST=Ran using default option and then tried -t chromiumorg/master and
saw a correct failure since I don't have that branch to track against.
Review URL: http://codereview.chromium.org/3032019
TEST=Tested with following workflow:
cros_mark_as_stable -p 'crash-reporter' -i 'boogabooga' commit
cros_mark_as_stable push
cros_mark_as_stable clean
Also passed in some real options for push_options in a branch that had nothing in it.
Review URL: http://codereview.chromium.org/3017002