Feature Customize Git Home

Hi @marin,

I'm back whit this change, which supersede my previous MR !39. This time, spec are fixed and new ones are added that check various place where git home can be customized. I touched comments about not changing attributes for app user and app root by adding "unless you know what you do".

If this MR gets merge in, it will resolve issue #12.

I'm currently doing the convergence of the recipe on CentOS and fetching opscode bento ubuntu base box. Will ping you when I finish convergence of the recipe on both system.

Regards,
Matt