Adds remaining functions to cros_mark_as_stable and cleaned up error messaging.
Adds remaining functions to cros_mark_as_stable and cleaned up error messaging.

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

mischief/scripts,fivethreeo/scripts,smilart/scripts,bcwaldon/coreos-scripts,zhang0137/scripts,zhang0137/scripts,andrejro/coreos--scripts,endocode/scripts,vmware/coreos-scripts,trnubo/scripts,gtank/scripts,fivethreeo/scripts,coreos/scripts,fivethreeo/scripts,glevand/coreos--scripts,bcwaldon/coreos-scripts,coreos/scripts,crawford/scripts,smilart/scripts,andrejro/coreos--scripts,BugRoger/scripts,crawford/scripts,nicescale/scripts,zhang0137/scripts,BugRoger/scripts,glevand/coreos--scripts,mjg59/scripts,mjg59/scripts,nicescale/scripts,sigma/coreos-scripts,marineam/coreos-scripts,crawford/scripts,trnubo/scripts,trnubo/scripts,sigma/coreos-scripts,nicescale/scripts,andrejro/coreos--scripts,BugRoger/scripts,endocode/scripts,vmware/coreos-scripts,mischief/scripts,mjg59/scripts,mischief/scripts,marineam/coreos-scripts,gtank/scripts,bcwaldon/coreos-scripts,smilart/scripts,gtank/scripts,endocode/scripts,vmware/coreos-scripts,sigma/coreos-scripts,marineam/coreos-scripts