Update spring to 1.6.4 to fix support for Bundler 1.11

Gemfile

@@ -278,7 +278,7 @@ group :development, :test do
   gem 'teaspoon', '~> 1.0.0'
   gem 'teaspoon-jasmine', '~> 2.2.0'
 
-  gem 'spring', '~> 1.3.6'
+  gem 'spring', '~> 1.6.4'
   gem 'spring-commands-rspec',    '~> 1.0.4'
   gem 'spring-commands-spinach',  '~> 1.0.0'
   gem 'spring-commands-teaspoon', '~> 0.0.2'

Gemfile.lock

@@ -763,7 +763,7 @@ GEM
       capybara (>= 2.0.0)
       railties (>= 3)
       spinach (>= 0.4)
-    spring (1.3.6)
+    spring (1.6.4)
     spring-commands-rspec (1.0.4)
       spring (>= 0.9.1)
     spring-commands-spinach (1.0.0)
@@ -1016,7 +1016,7 @@ DEPENDENCIES
   six (~> 0.2.0)
   slack-notifier (~> 1.2.0)
   spinach-rails (~> 0.2.1)
-  spring (~> 1.3.6)
+  spring (~> 1.6.4)
   spring-commands-rspec (~> 1.0.4)
   spring-commands-spinach (~> 1.0.0)
   spring-commands-teaspoon (~> 0.0.2)