README: update initialization instructions

With the Lua 5.2 port we change the way vicious is loaded as a module,
so that it remains backwards compatible with Lua 5.1 users. Also added
the author of the Lua 5.2 port to the contributors list.

README

@@ -35,7 +35,7 @@ your memory.
 
 Then add the following to the top of your rc.lua:
 
-  require("vicious")
+  local vicious = require("vicious")
 
 Once you create a widget (a textbox, graph or a progressbar) call
 vicious.register() to register it with Vicious:
@@ -559,3 +559,4 @@ Vicious contributors:
   - Hiltjo Posthuma          <hiltjo codemadness.org>
   - Hagen Schink             <troja84 googlemail.com>
   - Jörg Thalheim            <jthalheim gmail.com>
+  - Arvydas Sidorenko        <asido4 gmail.com>