update rails to 3.2.20

This is a security fix against a file existence exposure CVE-2014-7819

see:
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/

Conflicts:
	Gemfile.lock