Ruby version updated so it doesn't have the readline bug...

Ruby version updated so it doesn't have the readline bug https://www.ruby-lang.org/en/news/2014/05/09/ruby-2-0-0-p481-is-released/.

doc/install/installation.md

@@ -101,8 +101,8 @@ Remove the old Ruby 1.8 if present
 Download Ruby and compile it:
     mkdir /tmp/ruby && cd /tmp/ruby
-    curl --progress ftp://ftp.ruby-lang.org/pub/ruby/2.0/ruby-2.0.0-p353.tar.gz | tar xz
-    cd ruby-2.0.0-p353
+    curl --progress ftp://ftp.ruby-lang.org/pub/ruby/2.0/ruby-2.0.0-p481.tar.gz | tar xz
+    cd ruby-2.0.0-p481
     ./configure --disable-install-rdoc
     make
     sudo make install