Fix #302

Initializes gh_params and rh_params as empty lists in methods/common.py and
changes assertHead() in tests/methods/get.py to use passed argument, url. Fixes bug
where a HEAD request on a resource or item resulted in a server error.
Kelly Caylor
Merge branch 'kcaylor-iss302' into develop
Alphabetical order not an opinion
Merge branch 'develop' of https://github.com/nicolaiarocci/eve into develop

Sync to main version