Add support for loading in individual Flask modules

[dpford]

This adds the ability for sheer to use standalone Flask modules (more specifically, blueprints), loaded in via a blueprints.json file in the site's _settings folder.

To test it out, install the following packages inside your virtual environment:

pip install git+git://github.com/dpford/flask-govdelivery
pip install git+git://github.com/rosskarchner/govdelivery

Next, add the following to _settings/blueprints.json in your site:

{
  "flask_govdelivery":{
      "package" : "flask_govdelivery.govdelivery.controllers",
      "module" : "govdelivery"
    }
}

If all goes well, you should be able to go to the URL /form-test/ and get a success message, confirming the fact that the blueprint was loaded in, and the URL routes were setup.

[dpford]

Also, to run locally, this will require the environment variables outlined in the readme of this repo: https://github.com/dpford/flask-govdelivery

[rosskarchner]

This is pretty neat!