Added python-pip package

On most Ubuntu hosts you'll need to install pip before you can install
the registry.
Added instructions for installing on Red Hat-based systems
Merge pull request #34 from jamtur01/readmeupdates

Added python-pip package and Red Hat instructions
Added NewRelic support
Merge branch 'master' of github.com:dotcloud/docker-registry
Added dotcloudignore file
Add pidfile option to the golang implementation

This is required to handle docker-registry with startproc.
Merge pull request #35 from flavio/golang_impl_add_pidfile

Add pidfile option to the golang implementation