Abstracting away repeated logic
Dropped request.values usage

The dictionary `request.values` contains both querystring arguments and
POST/PUT body arguments. It's better to be explicit about where those values
should be coming from.
User model
User metadata
User resource
Smarter response
Documentation on Users
User tests
Token-based authentication
Added shiva-admin utility

This utility script will be used for some administration tasks like user
creation.