relax deps and prefer httpsig instead of http_signature
update to newer spec, based on httpsig implementation
Update to latest version of draft 3

  * Use (request-target) instead of (request-line)
  * Fix the tests
  * Add utils/sign3.py script to simplify adapting tests.
updated documentation
Merge pull request #1 from etoccalino/httpsig

Update to latest version of draft 3
Merge branch 'master' into httpsig

Conflicts:
	CHANGES.txt
	rest_framework_httpsignature/__init__.py
	setup.py
added a script to test installation
brought in fixes and update version
moved to httpsig for signing. upgrading package to 0.2.x