move package_ensure to params.pp

and set it to 'latest' on redhat releases 5.[01234].

redhat < 5.5 comes with sudo 1.6 which does not support the #includedir
directive. so we have to make sure we run the latest sudo version.
this will automatically update sudo to 1.7.2 on older releases.

nevertheless you have to have an updated version of sudo
available (e.g. satellite, rhn or a custom repo).
issue a warning if we are on redhat and the sudo version is < 1.7.2p1
import custom fact for the sudo version

currently only supports rhel. this is used to warn about sudo version <
1.7.2p1 on rhel.
use the anchor pattern for sudo::package in init.pp

sudo::conf requires sudo so we should anchor the sudo::package class.
otherwise resources declared in sudo::package may 'float' off.
comment why we set ensure to latest on rhel <= 5.4
rspec test for redhat 5.4 and package_ensure
fixed documentation for package_ensure on RHEL < 5.5
Update README.md

changed config_file_replace to false in the example where sudoers.d should be purged, but the sudoers file is left alone.
Add template for /etc/sudoers file
Merge pull request #62 from tosmi/rh5

better support for redhat 5 systems
Merge pull request #64 from tosmi/docfix

Update README.md
Merge pull request #66 from mremy/add_sudoers_template

Add template for /etc/sudoers file