Version bump to 0.7.4.
Version bump to 0.7.4.

  * 0.20.1 Ruby driver compatibility
  * descendants defaults to array
  * BSON::ObjectID#as_json
  * :fields now supports hash (:fields => {:content => 0, :title => 1})
  * one embeddable association
  * multiple symbol operators in query on one key now works (ie: {:age.gt => 10, :age.lt => 20} # => {:age => {'$gt' => 10, '$lt' => 20}})
  * many documents now accepts array of hashes (previously only array of association class objects)
  * bug fix for setting parent/root documents with embedded key
  * many association now keeps track of unsaved docs and saves them on owner save
  * updated validatable dependency
  * push_uniq now add_to_set and uses $addToSet (mongodb 1.3+)
  * unset modifier to remove keys from documents (mongodb 1.3+)

dhemmat/mongomapper,mongomapper/mongomapper,Yesware/mongomapper,kachick/mongomapper