Lock public_suffix to pre 1.5.0

The 1.5.0 version of public_suffix drops support
for ruby version < 2.0 which we still support.

gemfiles/rails32.gemfile

@@ -14,6 +14,7 @@ platforms :ruby, :mswin, :mingw do
 end
 
 group :test do
+  gem 'public_suffix', '< 1.5.0'
   gem 'capybara', '>= 2.0.3'
   gem 'minitest'
   gem 'minitest-rails'

gemfiles/rails40.gemfile

@@ -14,6 +14,7 @@ platforms :ruby, :mswin, :mingw do
 end
 
 group :test do
+  gem 'public_suffix', '< 1.5.0'
   gem 'capybara', '>= 2.0.3'
   gem 'minitest'
   gem 'minitest-rails'

tests/test_app/Gemfile

@@ -2,6 +2,7 @@ source 'https://rubygems.org'
 
 gem 'rails', '~> 3.2'
 gem 'rake', '< 11.0'
+gem 'public_suffix', '< 1.5.0'
 
 gem 'impressionist', :path => '../../'