flatmap implemented

Hi,

Just adding some of the implementation of the common helper function:

mapcat in clojure: http://clojuredocs.org/clojure_core/clojure.core/mapcat
flat_map in ruby: http://ruby-doc.org/core-2.0/Enumerable.html#method-i-flat_map
flatMap in  scala: http://www.scala-lang.org/api/current/index.html#scala.collection.mutable.Map

It is also the bind operator for the List monad: http://stackoverflow.com/questions/5436177/adding-haskells-monadic-bind-operator-to-scala

Cheers,
- Daniel