Allow custom nosetest parameters

The NOSETESTS variable can be used to support customizing the nosetests
parameters.  This allows providing custom nose parameters such as
--with-coverage.

Minor readme tweaks since I haven't edited this in a while.

Added ansible-vault to the installer

fix json typo in documentation

Various tests using datafiles are being moved into the integration test framework (tests_new right now).

The unit test infrastructure will remain for things that are mocked out and testable with out filesystem
side effects, and a few cases of things that might not be quite so much (like inventory) that can still
benefit from heavy access to the API.

See the 'tests_new/integration' directory, this will soon fold into tests_new.

we're a little further along the units directory will be reserved to pure-API tests.

We had some incorrect logic for when selinux is installed and disabled.

This occurred when a hash would be passed in via extra args and the
hash variable behavior was set to 'merge', which resulted in the
variable from extra args replacing the playbook variable.

copied over from the svn module.