upgrade rails for security vulnerability

http://weblog.rubyonrails.org/2014/10/30/Rails_3_2_20_4_0_11_4_1_7_and_4_2_0_beta3_have_been_released/
Merge remote-tracking branch 'origin/master' into rails-4.0.11

Conflicts:
	Gemfile.lock
add new stubs needed for polymorphic association
upgrade to rails 4.1.7
Merge pull request #78 from 18F/rails-4.1.7

upgrade to Rails 4.1.7