Added method to get all attributes regardless of initialization.

If the object is not persisted, the default values will be merged with
the current ones in the object making possible to overwrite the default
values in case the object has values for attributes with default values.
Fix build in 1.8.7

Array#each_with_object is not defined on ruby 1.8.7
Fixed Array Attribute Setter on ruby 1.8.7
Merge pull request #59 from zertico/get_all_attributes

Added method to get all attributes regardless of initialization.