Go path variables + package LWRP

I've extended the profile.d script to provide a default GOPATH and GOBIN, and I've added an LWRP for installing and updating packages. That resource should also allow for notification on actual updates.

To support package installation I've also added the git cookbook as a dependency; it may actually be worth changing that to be optional.

I'm very open to feedback, so just let me know. Thanks!