Both modules seboolean and zfs have not been adapted since they defer from the default (either by having a 'null' or special state, or prefering "on"/"off" for state indication.

Adds needs_update() method which will inspect the checkout for the
current revision and then the HEAD.  If the local check out is behind
HEAD, this will report changed=True and supply the revision numbers.

This updates the following modules to support check_mode:
* apt_key
* apt_repository
* easy_install
* pip - will always report changed due to the way it handles state
* seboolean
* selinux
* slurp - since nothing changes, it just adds that it supports
  check_mode
* subversion - reports changed when checking out new repo and
  when updating.
* supervisorctl
* svr4pkg

See issue #2114.

* Rename fail_on_rc_non_zero to check_rc, much more succinct.
* Simplify method defintion
* Fix command module and drop shell=shell option; whether to use
  shell is determined by if args is a list.

This updates apt, apt_repository, command, cron, easy_install, facter,
fireball, git, group, mount, ohai, pip, service, setup, subversion,
supervisorctl, svr4pkg, user, and yum to take advantage of run_command
in module_common.py.

  - Added username, password arguments.
  - Documented existing revision argument.
  - Corrected documentation/docstrings; removed git references, use svn
    nomenclature, etc.
  - Refactored duplicate code, redundant shell calls, filter abuse,
    inconsistent formating, etc.
  - Shell quoting so it doesn't break for one guy who has spaces in
    pathnames.
  - svn called with '--non-interactive' and '--no-auth-cache'.

Let our users determine what they want to do with a given module.
Particularily when the mdoule doesn't pose any such restrictions.

 - added terse syntax to modules.rst
 - added description of special variables to template module

Used os.path.expanduser on dest to allow e.g. ~/svn/repo as
a destination

added force option to git - made both subversion and git default to force=true for backward compatibility with git's previous behavior