[GEMS] Added rake as development dependency
Added the ability to define default values as lambdas

class Article
  include Redis::Persistence

  property :name
  property :created_at, :default => lambda { Time.now }
end

NOTE: Lambda is evaluated when the class instance is created
[REFACTOR] No need to compact same array twice
[REFACTOR] Don't call initialize when reloading instance with some aditional families, just update attributes