Update man pages and the message for an exception.

Added commit time information to the --version output

Now prints date of commit (and timezone offset of commit)
Hopefully resolves #783

Only run yum,apt through the with_items loop if there is a list of items.  Just a cosmetic fix on return values
for the most part.

Running ansible --version now outputs git information when the
repo lives in .git in the root of the ansible source (coping with the case
where the git info is elsewhere is left as an exercise).

This uses gitpython where installed, otherwise it interrogates the files
in the .git directory to get the same information.

The gitpython path could be removed, but then people might ask 'why did
you do it like this when gitpython exists'

add apt_repository module

add pip module

Add supervisorctl module

Add easy_install module

fix up yum state=latest with pkg groups

Make exception more specific (OSError) in setup module for selinux call

want to install an old package happy.

Abstract how to look up user password to be more flexible

Fix error handling when switching versions

Protect all selinux calls with try/except

This adds user_password() to abstract how the user's password is looked
up.  If spwd is not available, this will read the shadow file for the
user's shadow entry.  This will then facilitate idempotent password
changes on hosts without spwd.

Basically if umask is set to something like 0007 then chmod +r and chmod +x
are not the same as chmod a+r and chmod a+x

Using os.path.basename rather than source.split should make ansible more
portable (and even if never ported, more readable)