Remove more unused files
Add gitignore file for tmp and env directories
Simplify the directory structure

Now just using an app folder with the tools in the top level to make
importing strings a lot shorter.
Add Procfile for deployment to heroku
Add a settings file for keeping common constants

This can be overridden by adding a local_settings.py in the root
directory that overrides any of the constants.
Update app to use new settings file
Fix the Readmill api endpoint
Add local_settings.py to the gitignore
Improve robustness of file creation

Now using uuids for the filenames to avoid conflicts and removing
files one the request has finished. Tools still needs to be looked at.
Remove infuriating debug message when converting epub
Update requirements using `pip freeze`