Offset, TargetOffset and other options are not passed on the Tether

[talbet]

I cannot get the 'offset' option, which is documented in Tether, to work while using Drop. It looks like the Drop constructor calls the Tether constructor with a set of default options that are incorrectly merged with the parameters passed to the Drop constructor.

The Tether constructor is called here

      if (this.options.tetherOptions !== false) {
        this.tether = new Tether(extend({}, opts, this.options.tetherOptions));
      }

But this.options.tetherOptions will always be an empty object (it is initialised, but never referenced anywhere else in the code).

It looks like it should be merged with this.options instead?