enhanced current git user recognition

Replaces 'Bob Smith' & 'bob.smith@gmail.com' in prompt with the current global Git user's info when calling the 'gu' alias. If info is correct, user can hit enter twice and nothing changes (if sync-prompt returns empty strings the variables don't change). 

Instead of calling the separate 'gc' command, user can verify the Git user from inside the 'gu' function itself.