rc.lua: Call launcher() with a string

When awful.widget.launcher() is called with a string, it interprets it as the
path to an image and tries to load it. So why should we do the work of calling
image() ourselves if it can be done for us? ;)

Signed-off-by: Uli Schlachter <psychon@znc.in>

awesomerc.lua.in

@@ -64,7 +64,7 @@ mymainmenu = awful.menu({ items = { { "awesome", myawesomemenu, beautiful.awesom
                                   }
                         })
 
-mylauncher = awful.widget.launcher({ image = image(beautiful.awesome_icon),
+mylauncher = awful.widget.launcher({ image = beautiful.awesome_icon,
                                      menu = mymainmenu })
 -- }}}