Eliminate selector option in tooltip manager API

No packages use it currently, and it's really complex to support so
we should kill it while we have the chance. When it comes time to
rewrite the tooltip code or add features, not worrying about selectors
will make it easier.

src/tooltip-manager.coffee

@@ -122,6 +122,7 @@ class TooltipManager
       else if keystroke?
         options.title = getKeystroke(bindings)
 
+    delete options.selector
     options = _.defaults(options, @defaults)
     if options.trigger is 'hover'
       options = _.defaults(options, @hoverDefaults)