Use "Wand" for thumbnail generation

"Wand" (http://wand-py.org/) supports PSD files through ImageMagick's
MagickWand library.
Add a README containing a project description

This also includes all currently planned features.
Properly format README's nested list
Simple setup functionality

This will create a database and all needed directories with a single
command.
README's sublist changed to spaces as indent

This should hopefully fix the formating on github.
Add .gitignore
Don't overwrite saved files

If a file with the same name was uploaded the already existing file was
overwritten. We now upload to a temporary file first and then rename it
to the ID in the database after saving the File object in the database.
Don't let files be uploaded twice

We now save a hash for every file the find duplicates right when they
are uploaded.

We'll need to tell the user about this. For now it just shows the file
as being uploaded correctly, even though the response's status code
is 409 CONFLICT.
Don't import settings directly in tasks

Instead of importing marion.settings directly, we should use app.config
to have to possibility to overwrite the settings externally.
README's "Setup" styled better

Put the commands to run in a block so they are stand out more.
Merge branch 'master' into reactjs
Re-implement file upload
Re-implement image list