First stab at issue #111

But I think I need to tear this up and come at it from a different angle.
Progress on #111

Refactor the old check_public_key/has_public_key system and consolidate.  Also make the function applicable to testing private keys
compile
initial tests work
progress
a few bugs found in key pushing
New feature: don't sign pushes if the uid is of the right form.
keypulls seems to work now
Close #111
Close keybase/keybase-issues#37

Things were crashing if you didn't have any keys in your keyring