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.
`[ngannotate-rails]`(https://github.com/kikonen/ngannotate-rails) gem is awesome, and takes care of annotation.