Bump to 3.1.3

Gemfile.lock

 PATH
 PATH
   remote: .
   remote: .
   specs:
   specs:
-    paperclip (3.1.2)
+    paperclip (3.1.3)
       activemodel (>= 3.0.0)
       activemodel (>= 3.0.0)
       activerecord (>= 3.0.0)
       activerecord (>= 3.0.0)
       activesupport (>= 3.0.0)
       activesupport (>= 3.0.0)

lib/paperclip/version.rb

 module Paperclip
 module Paperclip
-  VERSION = "3.1.2" unless defined? Paperclip::VERSION
+  VERSION = "3.1.3" unless defined? Paperclip::VERSION
 end
 end