Ensure that an ExecJS runtime is available for realsies.

Fixes refinery#1512

templates/refinery/installer.rb

@@ -7,11 +7,21 @@
   require 'execjs'
   ::ExecJS::Runtimes.autodetect
 rescue
-  gsub_file 'Gemfile', "# gem 'therubyracer'", "gem 'therubyracer'"
+  require 'pathname'
+  if Pathname.new(destination_root.to_s).join('Gemfile').read =~ /therubyracer/
+    gsub_file 'Gemfile', "# gem 'therubyracer'", "gem 'therubyracer'"
+  else
+    append_file 'Gemfile', <<-GEMFILE
+
+group :assets do
+  # Added by Refinery. We want to ensure that you have an ExecJS runtime available!
+  gem 'therubyracer'
+end
+GEMFILE
+  end
 end
 
-append_file 'Gemfile' do
-"
+append_file 'Gemfile', <<-GEMFILE
 
 # Refinery CMS
 gem 'refinerycms', '~> #{VERSION_BAND}'
@@ -22,15 +32,14 @@
 #  gem 'refinerycms-inquiries', '~> #{VERSION_BAND}'
 #  gem 'refinerycms-search', '~> #{VERSION_BAND}'
 #  gem 'refinerycms-page-images', '~> #{VERSION_BAND}'
-"
-end
+GEMFILE
 
 run 'bundle install'
 rake 'db:create'
 generate "refinery:cms --fresh-installation #{ARGV.join(' ')}"
 
-say <<-eos
+say <<-SAY
   ============================================================================
     Your new Refinery CMS application is now installed and mounts at '/'
   ============================================================================
-eos
+SAY