engine missing adapter issue

gistfile1.rb

Started GET "/locomotive/hollow-briars-3788/preview/" for 127.0.0.1 at 2015-05-13 19:05:41 +0900
[LocomotiveCMS] [fetch site] host = local.dev / site_handle = "hollow-briars-3788"
  MOPED: 127.0.0.1:27017 QUERY        database=locomotive_engine_coal_dev collection=locomotive_sites selector={"$query"=>{"handle"=>"hollow-briars-3788"}
, "$orderby"=>{:_id=>1}} flags=[] limit=-1 skip=0 batch_size=nil fields=nil runtime: 1.0567ms
TODO: change content entry submission

LoadError - cannot load such file -- /home/dev/.rvm/gems/ruby-2.2.0@locomotive-engine/bundler/gems/steam-b626a219bf5c/lib/locomotive/steam/adapters/mongo
DB:
   () home/dev/.rvm/gems/ruby-2.2.0@locomotive-engine/bundler/gems/steam-b626a219bf5c/lib/locomotive/steam/repositories.rb:44:in `build_adapter'
   () home/dev/.rvm/gems/ruby-2.2.0@locomotive-engine/bundler/gems/steam-b626a219bf5c/lib/locomotive/steam/repositories.rb:11:in `block in <class:Reposit
ories>'