add unicorn: FAIL!

```git checkout unicorn```
**NOTE: not rackup or foreman start !! ?** => 
```
rails s # webrick
irb(main):001:0>  User.count
irb(main):001:0> User.count
D, [2013-12-03T18:41:49.586683 #14570] DEBUG -- :   MOPED: 54.226.71.234:10029 COMMAND      database=app19591881 command={:count=>"users", :query=>{}} runtime: 310.9270ms
Moped::Errors::OperationFailure: The operation: #<Moped::Protocol::Command
  @length=79
  @request_id=5
  @response_to=0
  @op_code=2004
  @flags=[]
  @full_collection_name="app19591881.$cmd"
  @skip=0
  @limit=-1
  @selector={:count=>"users", :query=>{}}
  @fields=nil>
failed with error "unauthorized"
  from /moped-2.0.0.beta4/lib/moped/operation/read.rb:50:in `block in execute'
  from /moped-2.0.0.beta4/lib/moped/node.rb:595:in `[]'
  from /moped-2.0.0.beta4/lib/moped/node.rb:595:in `block (2 levels) in flush'
  from /moped-2.0.0.beta4/lib/moped/node.rb:594:in `map'
  from /moped-2.0.0.beta4/lib/moped/node.rb:594:in `block in flush'
  from /moped-2.0.0.beta4/lib/moped/node.rb:618:in `block in logging'
  from /activesupport-4.0.2/lib/active_support/notifications.rb:159:in `block in instrument'
  from /activesupport-4.0.2/lib/active_support/notifications/instrumenter.rb:20:in `instrument'
  from /activesupport-4.0.2/lib/active_support/notifications.rb:159:in `instrument'
  from /moped-2.0.0.beta4/lib/moped/instrumentable.rb:31:in `instrument'
  from /moped-2.0.0.beta4/lib/moped/node.rb:617:in `logging'
  from /moped-2.0.0.beta4/lib/moped/node.rb:588:in `flush'
  from /moped-2.0.0.beta4/lib/moped/node.rb:392:in `process'
  from /moped-2.0.0.beta4/lib/moped/operation/read.rb:48:in `execute'
  from /moped-2.0.0.beta4/lib/moped/node.rb:649:in `read'
  from /moped-2.0.0.beta4/lib/moped/node.rb:90:in `command'
... 7 levels...
  from /moped-2.0.0.beta4/lib/moped/read_preference/selectable.rb:65:in `call'
  from /moped-2.0.0.beta4/lib/moped/read_preference/selectable.rb:65:in `with_retry'
  from /moped-2.0.0.beta4/lib/moped/read_preference/primary.rb:54:in `with_node'
  from /moped-2.0.0.beta4/lib/moped/database.rb:72:in `command'
  from /moped-2.0.0.beta4/lib/moped/query.rb:41:in `count'
  from /Users/pb/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/bundler/gems/mongoid-f8b439dd9a59/lib/mongoid/contextual/mongo.rb:60:in `block in count'
  from /Users/pb/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/bundler/gems/mongoid-f8b439dd9a59/lib/mongoid/contextual/mongo.rb:449:in `try_cache'
  from /Users/pb/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/bundler/gems/mongoid-f8b439dd9a59/lib/mongoid/contextual/mongo.rb:60:in `count'
  from /Users/pb/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/bundler/gems/mongoid-f8b439dd9a59/lib/mongoid/contextual.rb:19:in `count'
  from /Users/pb/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/bundler/gems/mongoid-f8b439dd9a59/lib/mongoid/findable.rb:49:in `count'
  from (irb):1
  from /railties-4.0.2/lib/rails/commands/console.rb:90:in `start'
  from /railties-4.0.2/lib/rails/commands/console.rb:9:in `start'
  from /railties-4.0.2/lib/rails/commands.rb:62:in `<top (required)>'
  from bin/rails:4:in `require'
  from bin/rails:4:in `<main>'irb(main):002:0> 
```