Bump poltergeist to `~> 1.9.0`

Gemfile

@@ -273,7 +273,7 @@ group :development, :test do
 
   gem 'capybara',            '~> 2.4.0'
   gem 'capybara-screenshot', '~> 1.0.0'
-  gem 'poltergeist',         '~> 1.8.1'
+  gem 'poltergeist',         '~> 1.9.0'
 
   gem 'teaspoon', '~> 1.0.0'
   gem 'teaspoon-jasmine', '~> 2.2.0'

Gemfile.lock

@@ -552,7 +552,7 @@ GEM
     parser (2.2.3.0)
       ast (>= 1.1, < 3.0)
     pg (0.18.4)
-    poltergeist (1.8.1)
+    poltergeist (1.9.0)
       capybara (~> 2.1)
       cliver (~> 0.3.1)
       multi_json (~> 1.0)
@@ -978,7 +978,7 @@ DEPENDENCIES
   org-ruby (~> 0.9.12)
   paranoia (~> 2.0)
   pg (~> 0.18.2)
-  poltergeist (~> 1.8.1)
+  poltergeist (~> 1.9.0)
   pry-rails
   quiet_assets (~> 1.0.2)
   rack-attack (~> 4.3.1)