Add development dependency sprite-factory

Gemfile

@@ -348,6 +348,8 @@ group :development do
 
   # thin instead webrick
   gem 'thin', '~> 1.8.0'
+
+  gem 'sprite-factory', '~> 1.7'
 end
 
 group :development, :test do

Gemfile.lock

@@ -1214,6 +1214,7 @@ GEM
     spring (2.1.1)
     spring-commands-rspec (1.0.4)
       spring (>= 0.9.1)
+    sprite-factory (1.7.1)
     sprockets (3.7.2)
       concurrent-ruby (~> 1.0)
       rack (> 1, < 3)
@@ -1620,6 +1621,7 @@ DEPENDENCIES
   spamcheck (~> 0.1.0)
   spring (~> 2.1.0)
   spring-commands-rspec (~> 1.0.4)
+  sprite-factory (~> 1.7)
   sprockets (~> 3.7.0)
   sshkey (~> 2.0)
   stackprof (~> 0.2.15)