Add $mirror_url parameter to a few common repos

This adds the parameter $mirror_url to the repo classes for CentOS 6,
CentOS 5, Scientific Linx and EPEL.  It's intended to allow the use of
local mirrors through Puppet 3.x databinding.

The parameter takes a "clean" URL to the base of the mirroring
infrastructure for each class, e.g., rsync://msync.centos.org::CentOS
for CentOS.  After checking it agains a regex for clean URLs, it then
interpolates with the known directory structure to create `basedir`
variables for each repo.  The `failovermethod` parameter is set to
`priority` for each repo to avoid round-robin behavior with the existing
`mirrorlist`.
Merge pull request #27 from lamawithonel/private_mirrors

Add $mirror_url parameter to a few common repos
Added remi-php55 for PHP 5.5
Removed other remi repo from remi-php55
Merge pull request #29 from gavroche/master

Added remi-php55 for PHP 5.5
Removed security plugin
Release tagged and published to the Forge
Updated Geppetto project file
Release v2.1.6
Rename class that is SL6-specific.
Add class for configuring sl5x repos.
Delete file that was renamed to sl6.pp
Load release-specific Scientific Linux class.
Update README about SL5 support.
Merge pull request #30 from gwarf/add_sl5_support

Add sl5 support
Add Ganeti repo from http://jfut.integ.jp/linux/ganeti/
Add $yum::extrarepo logic for yum::repo::integ_ganeti
Merge pull request #32 from lamawithonel/integ_ganeti

Add Ganeti repo from http://jfut.integ.jp/linux/ganeti/
Add a managed repo definition for the ELRepo.org repos
Merge pull request #33 from lamawithonel/elrepo

Add a managed repo definition for the ELRepo.org repos