[#3] Respect default_format for rabl response

lib/grape-rabl/formatter.rb

@@ -13,6 +13,7 @@ def after
         rabl(current_endpoint) do |template|
           engine = ::Tilt.new(view_path(template))
           rendered = engine.render(current_endpoint, {})
+          headers['Content-Type'] = content_types[env['api.format']]
           Rack::Response.new(rendered, status, headers).to_a
         end
       end

spec/grape_rabl_spec.rb

@@ -16,11 +16,18 @@ def app; subject end
     lambda{ get "/home" }.should raise_error("Use Rack::Config to set 'api.tilt.root' in config.ru")
   end
 
+
   context "titl root is setup"  do
     before do
       subject.before { env["api.tilt.root"] = "#{File.dirname(__FILE__)}/views" }
     end
 
+    it "should respond with proper content-type" do
+      subject.get("/home", :rabl => "user"){}
+      get("/home")
+      last_response.headers["Content-Type"].should == "application/json"
+    end
+
     it "should not raise error about root directory" do
       subject.get("/home", :rabl => true){}
       lambda{ get "/home" }.should_not raise_error("Use Rack::Config to set 'api.tilt.root' in config.ru")