Fix script that runs tests against all available Gemfiles

BUNDLE_GEMFILE needs the full path to work properly.

Load all custom Gemfiles rather than a fixed list, so adding/removing
files from the gemfiles/ folder just works.

test/run_all.rb

@@ -3,19 +3,19 @@ def bundle_check
 end
 
 command  = 'ruby -w -Ilib -Itest test/all.rb'
-gemfiles = %w(gemfiles/Gemfile.rails-3.x gemfiles/Gemfile.rails-2.3.x gemfiles/Gemfile.no-rails)
+gemfiles = %w(Gemfile) + Dir['gemfiles/Gemfile*'].reject { |f| f.end_with?('.lock') }
 
 results = gemfiles.map do |gemfile|
   puts "BUNDLE_GEMFILE=#{gemfile}"
-  ENV['BUNDLE_GEMFILE'] = gemfile
+  ENV['BUNDLE_GEMFILE'] = File.expand_path("../../#{gemfile}", __FILE__)
 
   unless bundle_check
     puts "bundle install"
     system('bundle install')
   end
 
   puts command
-  system('ruby -w -Ilib -Itest test/all.rb')
+  system command
 end
 
 exit(results.inject(true) { |a, b| a && b })