TODO: Generic UNIX backend

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

TODO.md

@@ -1,6 +1,8 @@
 LibuEv TODO
 ===========
 
+* Add standard UNIX backend with select() and timer_create()
+  See SMCRoute and toolbox for examples.
 * Port to *BSD kqueue API, http://en.wikipedia.org/wiki/Kqueue
   Also in UNIX Network Progamming, by W. Richard Stevens 3rd ed.
 * Restore Lua bindings now that libuEv itself has stabilized