Specify which branch is to be returned.
Reflect changes to 'development_branch' in rest of code.

Instead of using the previously hardcoded 'stable' branch - grab it via
the get_branch function. development_branch no longer exists; use
get_branch('development') to grab the development branch.
Shell escape 'branch' var.

This is used in a shell command so it must be cleaned up before actually
using it in the command.
Merge unhardcode-stable (#103) into master

Un-hardcode stable and development branch.

This will allow devs to specify whatever branch they prefer for their
project rather than using the default 'master' and 'stable' branches for
development and stable purposes.

This also means the stable branch is no longer hardcoded.