Use full entity name as a default (fixes #779)

I just wanted to resolve this:

```
- model.to_s.split('::').last
+ model.to_s
```

But I met a problem that it receives Class type in here
https://github.com/ruby-grape/grape-swagger/blob/8abddd5f2ce5fe29238990b136625f34371b0be0/lib/grape-swagger/endpoint.rb#L354
But String type in the another place, where the type is generated. So,
splitting and taking the last actually returns the same as `name`
method of the class. That is very strange I think.

Also, if we, for example, use such constructions, we end up with just
`V1` and `V2` fron the `A::B` module as they are parsed first:

```ruby
module A
  module B
    class V1 < Grape::Entity
     ...

    class V2 < Grape::Entity
     ...

module A
  module C
    class V1 < Grape::Entity
      ...

    class V2 < Grape::Entity
      ...
```

This PR fixes this issue.

Author: mrexox

lib/grape-swagger/doc_methods/data_type.rb

@@ -51,11 +51,11 @@ def parse_entity_name(model)
           if model.methods(false).include?(:entity_name)
             model.entity_name
           elsif model.to_s.end_with?('::Entity', '::Entities')
-            model.to_s.split('::')[-2]
-          elsif model.respond_to?(:name)
-            model.name.demodulize.camelize
+            model.to_s.split('::')[0..-2].join('::')
+          elsif model.to_s.start_with?('Entity::', 'Entities::')
+            model.to_s.split('::')[1..].join('::')
           else
-            model.to_s.split('::').last
+            model.to_s
           end
         end
 

lib/grape-swagger/endpoint.rb

@@ -345,7 +345,6 @@ def expose_params_from_model(model)
         raise GrapeSwagger::Errors::SwaggerSpec,
               "Empty model #{model_name}, swagger 2.0 doesn't support empty definitions."
       end
-
       @definitions[model_name] = GrapeSwagger::DocMethods::BuildModelDefinition.build(model, properties, required)
 
       model_name

spec/issues/427_entity_as_string_spec.rb

@@ -35,5 +35,5 @@ class RoleEntity < Grape::Entity
     JSON.parse(last_response.body)['definitions']
   end
 
-  specify { expect(subject.keys).to include 'RoleEntity', 'WithoutRole' }
+  specify { expect(subject.keys).to include 'RoleEntity', 'Permission::WithoutRole' }
 end

spec/issues/430_entity_definitions_spec.rb

@@ -82,11 +82,11 @@ class NameApi < Grape::API
     JSON.parse(last_response.body)['definitions']
   end
 
-  specify { expect(subject).to include 'Class1' }
-  specify { expect(subject).to include 'Class2' }
+  specify { expect(subject).to include 'TestDefinition::DummyEntities::WithVeryLongName::AnotherGroupingModule::Class1' }
+  specify { expect(subject).to include 'TestDefinition::DummyEntities::WithVeryLongName::AnotherGroupingModule::Class2' }
   specify { expect(subject).to include 'FooKlass' }
-  specify { expect(subject).to include 'FourthEntity' }
-  specify { expect(subject).to include 'FithEntity' }
+  specify { expect(subject).to include 'TestDefinition::DummyEntities::WithVeryLongName::AnotherGroupingModule::Class4::FourthEntity' }
+  specify { expect(subject).to include 'TestDefinition::DummyEntities::WithVeryLongName::AnotherGroupingModule::Class5::FithEntity' }
   specify { expect(subject).to include 'BarKlass' }
-  specify { expect(subject).to include 'SeventhEntity' }
+  specify { expect(subject).to include 'TestDefinition::DummyEntities::WithVeryLongName::AnotherGroupingModule::Class7::SeventhEntity' }
 end

spec/swagger_v2/api_swagger_v2_param_type_body_spec.rb

@@ -189,7 +189,7 @@ def app
         'type' => 'object',
         'properties' => {
           'data' => {
-            '$ref' => '#/definitions/ApiResponse',
+            '$ref' => '#/definitions/NestedModule::ApiResponse',
             'description' => 'request data'
           }
         },
@@ -207,7 +207,7 @@ def app
     end
 
     specify do
-      expect(subject['definitions']['ApiResponse']).not_to be_nil
+      expect(subject['definitions']['NestedModule::ApiResponse']).not_to be_nil
     end
 
     specify do