Suppress warnings that phantomjs was not installed system-wide

An according pull request was made upstream at
colszowka/phantomjs-gem#61

spec/features/feature_spec_helper.rb

@@ -17,6 +17,17 @@
 
 require_relative "../../lib/machinery"
 
+# Suppress phantomjs-gem warning about phantomjs not being installed system-wide
+require 'phantomjs'
+module Phantomjs
+  class Platform
+    def self.system_phantomjs_path
+      `which phantomjs 2> /dev/null`.delete("\n")
+    rescue
+    end
+  end
+end
+
 require "byebug"
 require "rspec-steps"
 require "capybara/rspec"