upgrade rspec-rails to 4.0 to fix WrongScopeError

See rspec/rspec-rails#2417

Gemfile

@@ -88,7 +88,7 @@ group :development, :test do
   gem "sqlite3"
 
   # add rspec
-  gem "rspec-rails", "~> 3.8"
+  gem "rspec-rails", "~> 4.0"
   gem "capybara"
   gem "database_cleaner"
   gem "rspec-snapshot"

Gemfile.lock

@@ -362,14 +362,14 @@ GEM
     rspec-mocks (3.9.1)
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.9.0)
-    rspec-rails (3.9.1)
-      actionpack (>= 3.0)
-      activesupport (>= 3.0)
-      railties (>= 3.0)
-      rspec-core (~> 3.9.0)
-      rspec-expectations (~> 3.9.0)
-      rspec-mocks (~> 3.9.0)
-      rspec-support (~> 3.9.0)
+    rspec-rails (4.0.1)
+      actionpack (>= 4.2)
+      activesupport (>= 4.2)
+      railties (>= 4.2)
+      rspec-core (~> 3.9)
+      rspec-expectations (~> 3.9)
+      rspec-mocks (~> 3.9)
+      rspec-support (~> 3.9)
     rspec-snapshot (2.0.3)
       awesome_print (> 1.0.0)
       rspec (> 3.0.0)
@@ -509,7 +509,7 @@ DEPENDENCIES
   rails (~> 6.0)
   rails-controller-testing
   random_data
-  rspec-rails (~> 3.8)
+  rspec-rails (~> 4.0)
   rspec-snapshot
   rubocop (~> 1.22.1)
   rubocop-rails