Add specs for String coercion

Author: stanhu

spec/grape/validations/validators/coerce_spec.rb

@@ -180,6 +180,23 @@ def self.parsed?(value)
         expect(last_response.body).to eq(integer_class_name)
       end
 
+      it 'String' do
+        subject.params do
+          requires :string, coerce: String
+        end
+        subject.get '/string' do
+          params[:string].class
+        end
+
+        get '/string', string: 45
+        expect(last_response.status).to eq(200)
+        expect(last_response.body).to eq('String')
+
+        get '/string', string: nil
+        expect(last_response.status).to eq(200)
+        expect(last_response.body).to eq('NilClass')
+      end
+
       it 'is a custom type' do
         subject.params do
           requires :uri, coerce: SecureURIOnly