Change API authentication to hosted mist.io service

First time you fill in email and password and io recieves
a token that is saved in db.yaml and is later on used to
compose an authentication header added to HTTP requests
towards https://mist.io/. The hashed password is no longer
saved in db.yaml.
Merge branch 'staging' into api_auth_changes

Conflicts:
	src/mist/io/views.py
Merge pull request #55 from mistio/api_auth_changes

Change API authentication to hosted mist.io service