Adds New Form Validation

Adds validation to the games.new form so errors display after you
submit the form and then auto-clear as you correct them.
Add Publisher Association and Routes

Adds a publisher model and relationship to games. Games belongTo a
publisher and a publisher hasMany games. Adds a games resource with
index and details routes. Adds link to games page to link to the
publisher page. The publisher page also has a list of games that
links back to games.details. Adds publisher select box to games.new.