Update 'associationDetails' & 'get' methods to retrieve polymorphic 'belongsTo' associations as per new representation in Brainstem
Added polymorphic belongs to association example to readme
Bumped version
Updated gemfile lock with new gem version
Added polymorphic belongs to support to 'Brainstem.Model#associationsAreLoaded'
Updated UserFileAssociation builder to use polymorphic asset_object association
Merge pull request #34 from mavenlink/update_polymorphic_belongs_to

Add support for polymorphic "belongs to" associations