Added the overwrite option to gitcheckout

This is a useful option to have, so I thought I'd add it. Includes unit test & README updates.
Added the "--force" option to gitpush

Another useful flag to have access to. Includes unit test and README updates.
Merge pull request #50 from sedge/dashBee

Added extra 'checkout' and 'push' functionality
Release v0.2.10