underscore JSONAPI::Resource#module_path when deriving from name
underscore JSONAPI::Resource#module_path when deriving from name

Using downcase does not have the intended effect. For example, a 
resource with name 'MyModuleNameSpace::NamespacedResource' previously 
had a module_path of 'mymodulenamespace'. Using underscore the 
module_path for 'MyModuleNameSpace::NamespacedResource' is 
'my_module_name_space'.
cover/jsonapi-resources,garytaylor/jsonapi-resources,iamvery/jsonapi-resources,danielma/jsonapi-resources,kevintraver/jsonapi-resources,CheckMateIO/jsonapi-resources,togglepro/jsonapi-resources,Skeduna/jsonapi-resources,jashank/jsonapi-resources,AKHarris/jsonapi-resources,jsmestad/jsonapi-resources,datapipe/jsonapi-resources,sozuuuuu/jsonapi-resources,localytics/jsonapi-resources,harisadam/jsonapi-resources,dphaener/jsonapi-resources,debreczeni/jsonapi-resources,cerebris/jsonapi-resources,senid231/jsonapi-resources