Prepare pom.xml for Sonatype inclusion

According to Sonatype requirements specified here http://central.sonatype.org/pages/requirements.html#correct-coordinates
the groupId of the project should match the package prefix, so we change it to com.spotify.crunch

Github ownership has been transferred from me (DavW) to the spotify organisation, so the scm has been changed to reflect that

Added name, description, developers and licenses blocks as required by Sonatype