Manage Django, Boto, Python-cloudfiles and Django-storages as external libraries

[benoitbryon]

See #6 and #86.

This pull request is based on #81 codebase, so #81 may be merged before this one:

• the application is packaged as an egg (#81)
• Django, Boto and Python-cloudfiles are external dependencies (see #86 and dependencies-external branch)
• Django-storages is an external dependency (see #6 and dependencies-external-storages branch

I froze version numbers in a restrictive way, to match the version that was included in fileconveyor. Maybe external librairies can be upgraded. But it should be another task.

I couldn't test every storage: I did my best to avoid import errors, but I cannot guarantee that transporters and storages actually work. So feedback is welcome.

[wimleers]

Tested with:

 pip install -e git+file:///Users/wimleers/Work/fileconveyor#egg=fileconveyor

… I was impressed that this actually works. I based this command off of your explanation in #81, and it really just works! Awesome!

I'm super excited to commit this in a few seconds… Thank you so much for your awesome contributions! :)