Update get_url

Small syntactic correction: Removed trailing double-quote from example.
slurp: import base64 as module_common no longer does
host.get_variables includes too many variables, use host.vars instead

Not quite as attractive, but allows variable precedence and lazy
resolution to work as intended, rather than resolving them on a
per-inventory basis.
Merge pull request #2271 from MWGriffin/patch-1

Update get_url
Fix parse_kv invocation in group_by to use imported name

Fixes #2277.
Teach makefile to accept different versions of python

This commit makes the Makefile nicer for packagers so they can select versions
of python. E.g. on a RHEL5 system with Python2.6 (installed from EPEL)

	make PYTHON=python2.6 install