Pass the correct options to when calling a plugin

We were passing the wrong options to the plugin itself, meaning that any options configued in the Brocfile were not being passed to the plugin. This fixes that problem.

@rjackson I looked at adding a test for this, but it didn't look like we were testing the `toTree` call anywhere yet. Before pulling it in, want to pair sometime this evening or tomorrow on adding a test for this?