Put needed packages in requirements.txt

All the required packages are now in requirements.txt for easy
installation in a virtual environment
Putting all needed packages in a virtualenv makes it much simpler to
handle dependencies.

Add debug toolbar
Add SQLite databases to gitignore
Change default settings to use SQLite

Since SQLite is embedded in Python and doesn't require a server, it is
much easier to use for development or local installations.
Add install instructions
Remove trailing whitespace
Merge pull request #68 from antoinealb/master

Add install instructions