Add gist commads to keymaps

leader g for creating a public gist
leader gp for private gist

This requires the gist gem
`gem install gist`

Amos King @adkron <amos.l.king@gmail.com>
Remove keymap confilict between git push and gist

private gist is now leader pg

Amos King @adkron <amos.l.king@gmail.com>