Add user_update_permission to list of defaults
Add SSOPushCredential class

This takes a predefined user for permission syncing,
creates the required authorisations and permissions,
and returns the correct bearer token for the 
application we're making the request to.
Change SSOPushClient to obtain credentials from SSOPushCredential

SSOPushClient will now use the bearer token returned
from SSOPushCredential for the particular application
we want to push to.
Reset the cached user before and after each test
Move the "user_update_permission" out of the default list

It seems semantically correct to have this permission
in the list of supported permissions, but not the
list of defaults, as the purpose of the default list 
is ambiguous and could be interpreted to suggest
that they should be given to any authorised user.
Add initializer for the SSO push user email address

Replace the existing gds_api_credentials initializer
with a new config for the SSO push user.
Revert "Add a rake task to grant permissions to the sync user"

This is no longer needed as SSOPushCredential ensures
the correct authorisations and permissions are in place
on an app-by-app basis.

This reverts commit 270e39675500c1b77fae404b20cdafc4fa4359e8.

Conflicts:
	lib/tasks/api_clients.rake
Merge pull request #91 from alphagov/sync-with-bearer-tokens

Sync SSO permissions and suspensions using bearer tokens