Correct Gerrit documentation link

The documentation was moved, so update the link.

Also change the link to refer to the documentation to refer
to Gerrit 2.8 which is now the latest major version.

Change-Id: I07d55521b52806f09130bcb6673a354e241f2c92
Accept kwargs for request functions

kwargs now made passable to request functions so that lower-level
python-requests interface can be fully utilized.

Change-Id: I38eff49314a3966546e0b272af2e58ed276269d9
Version 0.2.4

Change-Id: I65d45f11f3b467f4cf8bc34a4a63749406d78abf