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.

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.

This allows flexible selection of the Python version to use while
creating the virtualenv.

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

  - .rst now supresses default if none is set (looks better in HTML)
  - .rst now handles empty options list
  - Fixed postgresql_user and mysql_user because YAML contained colons
  - docs for facter

Added required as optional argument to get_bin_path(). It defaults to
false.  Updated following modules to use required=True when calling
get_bin_path():  apt_repository, easy_install, group, pip,
supervisorctl, and user.
Also removed _find_supervisorctl() from supervisorctl module and updated
_is_running() to not need it.

* Migraed easy_install, pip, service, setup, and user.
* Updated fail_json message in apt_repository
* Fixed easy_install to not hardcode location of virtualenv in
  /usr/local/bin/.
* Made handling of virtualenv more consistent between easy_install and
  pip.

mpdehaan requested in ansible/ansible#795 that globals be removed.
The response was to remove the lines with the word 'global', but not
the actual use of global variables.  Which makes the module break silently.
Updated to use local variables.