Add chkconfig to install and uninstall scripts for RPMs

Addresses: #110

This adds the app to chkconfig in the post install script, and
likewise removes it in the uninstall step.  It is based
on the usage documented at
http://fedoraproject.org/wiki/Packaging%3aScriptletSnippets
Merge pull request #112 from basho/jem-rhel-chkconfig

Add chkconfig to install and uninstall scripts for RPMs