Requires fabric to run.
Stub file parsing is utilising drush make code at moment so that has to be 
installed and configured in the php script.

Usage:
  fab build:stub=http://some/stubfile.build

TODO
----

- make sure return 0/1 for jenkins
- make site uri an argument
- break out migration steps to optional functions
- add error handling for each migration step
- option to delete previous platform if no sites exist on it
- if site doesn't exist, then provision it
- optional rollback if a migration step fails