ruby: v↑ ruby2.1 (2.1.7)

Ruby 2.1.7 contain security and other bugfixes:

    https://www.ruby-lang.org/en/news/2015/08/18/ruby-2-1-7-released/

/reviewed-by @kazuhiko  (on nexedi/slapos!28)

component/ruby/buildout.cfg

@@ -26,8 +26,8 @@ environment =
 
 [ruby2.1]
 <= ruby-common
-url = http://ftp.ruby-lang.org/pub/ruby/2.1/ruby-2.1.6.tar.xz
-md5sum = ec6f10ca331ce947802ede86259513a8
+url = http://ftp.ruby-lang.org/pub/ruby/2.1/ruby-2.1.7.tar.xz
+md5sum = 2e43a1d32cc16975a6b5d3ffce399199
 
 
 [ruby2.2]