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.
Revert "Fix #302"

This reverts commit 7c3eee944c0b60a86be7b491b446e9bb9f2e3939.
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