Add Angular Best Practices

A first crack at some Angular best practices arrived at through a seven month
angular project and discussions with other teams doing angular work around the
company. I'm no angular expert, but these are practices I can remember working
well, particularly in the face of other options that *did not* work equally
well.
Maybe reword to something like: "If you desire a singleton, wrap your class in a factory function and return a new instance of that class from that function"?