Add ability to create and push to github

Requires the github cli "Hub".
Consolidate the code for heroku bitbucket github.

Before they were each split to some code at the beginning and some at the
end. Moved everything to the end.
Code clean up and refactoring

- use options[:organization] instead of Maguro.organization.
- remove lib/maguro.rb since we can directly call Maguro::Features from
maguro/app_genreator.rb, and no longer use Marguro.organization
- remove template.rb since this is no longer a file that we pass into
rails as a rails template. Now we directly call maguro new.