Updated "gps" and "gpp" aliases to use "deploy" branch.

* The use of "stage" and "production" branches added additional
  complexity that wasn't always necessary.
Added "gbc" function to create and switch to a new local branch.

* Usage: gbc <branch>
Added --set-upstream option to "gpo" alias.

* The "gpo" alias is generally used to push a new branch to remote
  repo. This sets additional tracking so that "gp" can be used for
  future pushes to the new remote branch.