Always set sortkey in Change object

The from_json method returns None if the key does not exist
in the json data, so we don't need to check for existence of
the key when constructing the object.

This also ensures that the constructed object has a sortkey
member.

Change-Id: Ic342f8b25aeded0e999f93fa29190853354c57f0
Include change status in Change object

Change-Id: I188e4cc116878cdd6679e45bf3ee545b20ce974e
Add support for CurrentPatchSet

The "currentPatchset" field of the query results includes information
about the review label scores.

Change-Id: I41d54225284e15b2b61b79bfaa309cd5c2b4b86a
Add user in the Approval object

Include the account information for the user who gave the
approval.

Change-Id: I3857c9913c38a5c5223111274314e107f4c81090
Release notes for 0.2.2

Change-Id: I57db6ab987ac604134267ccc79ec4451a0119841
Bump version to 0.2.2

Change-Id: I32b970452809d31037ad15783d2f50e894e530ed