Enable readline for python

Needed for git as well.

options.conf.d/system.conf

@@ -14,7 +14,7 @@ x11-drivers/nvidia-drivers tools
 
 sys-auth/ConsoleKit2 cgroups polkit
 
-dev-lang/python tk
+dev-lang/python tk readline
 
 # needed for valgrind
 sys-libs/glibc build_options: symbols=preserve