Initial staging for 0.5.0 release

[mizzao]

Features to merge:

• Turkserver.treatment on the server #89
• Refresh assignment continues on exceptions #92

List of things to do to get this out on Atmosphere:

• Finalize package name and version that will be published (mizzao:[email protected], this needs to be reverted from before).
• Create a History.md that will track significant changes from now on.
• Change install instructions to remove git clone command.
• Make some contribution guidelines (can add more later).
• Update various URL references.

Once released:

• Update tutorial app to reference published package.
• Update API and guide to refer to easier install.