Add bin directory to avoid seeing bin files

These get generated by bundle binstubs command
Changes for Zeus with RubyMine + Rails 4 Tutorial

1. Add gems
2. Remove all references to Spork (aka drb) in
   a) .rspec (drb)
   b) Guardfile
   c) spec_helper.rb
3. Remove autorun reference in spec_helper
Merge branch 'zeus' into demo

* zeus:
  Changes for Zeus with RubyMine + Rails 4 Tutorial
  Add bin directory to avoid seeing bin files
Rename correct_user to correct_micropost
Add update method to show refactorings of micropost_params

NOTE: update is not tested nor used.