Add swift to plugin template

[n8henrie]

I've added some boilerplate for using Swift in plugins to this project in the swift branch.

If anyone wants to check it out, you should be able to run:

$ cookiecutter 'https://github.com/quicksilver/plugin_template' --checkout swift

afterwards should be able to run the tests and see several actions for text objects that come up when searching for “swift”.

Please let me know if anyone can give it a shot! Will also start an issue.