Replace timecop with the rails builtin travel_to method

Gemfile

@@ -113,7 +113,6 @@ group :test do
   gem "minitest", "~> 5.1", :platforms => [:ruby_19, :ruby_20]
   gem "rails-controller-testing"
   gem "rubocop"
-  gem "timecop"
   gem "webmock"
 end
 

Gemfile.lock

@@ -319,7 +319,6 @@ GEM
     thor (0.19.4)
     thread_safe (0.3.6)
     tilt (2.0.7)
-    timecop (0.9.0)
     tins (1.14.0)
     tzinfo (1.2.3)
       thread_safe (~> 0.1)
@@ -397,11 +396,10 @@ DEPENDENCIES
   sanitize
   sass-rails (~> 5.0)
   secure_headers
-  timecop
   uglifier (>= 1.3.0)
   validates_email_format_of (>= 1.5.1)
   vendorer
   webmock
 
 BUNDLED WITH
-   1.12.5
+   1.13.7

test/controllers/api_controller_test.rb

@@ -304,7 +304,7 @@ class ApiControllerTest < ActionController::TestCase
     # nodes with a different timestamp should be ignored
     create(:node, :timestamp => Time.utc(2008, 1, 1, 0, 0, 0), :lat => 7, :lon => 7)
 
-    Timecop.freeze(Time.utc(2010, 4, 3, 10, 55, 0))
+    travel_to Time.utc(2010, 4, 3, 10, 55, 0) do
       get :changes
       assert_response :success
       now = Time.now.getutc
@@ -314,9 +314,9 @@ class ApiControllerTest < ActionController::TestCase
           assert_select "tile", :count => 0
         end
       end
-    Timecop.return
+    end
 
-    Timecop.freeze(Time.utc(2007, 1, 1, 0, 30, 0))
+    travel_to Time.utc(2007, 1, 1, 0, 30, 0) do
       get :changes
       assert_response :success
       # print @response.body
@@ -329,7 +329,7 @@ class ApiControllerTest < ActionController::TestCase
           assert_select "tile", :count => 6
         end
       end
-    Timecop.return
+    end
   end
 
   def test_changes_zoom_invalid