Modifying ast plugin should bust cache

[asakusuma]

Given an addon that has an htmlbars-ast-plugin, cached htmlbars files should be busted when the plugin is modifyed. This does not happen. I have to delete the async cache.

// Changing this file should bust the cache
var ReWriteStuff = require('re-write-stuff');

module.exports = {
  name: 'my-addon',
  setupPreprocessorRegistry: function() {
    registry.add('htmlbars-ast-plugin', {
      name: 're-write-stuff',
      plugin: ReWriteStuff
    });
  }
};

[rwjblue]

@asakusuma - Confirm. I would like to do the same thing that we decide on in babel/broccoli-babel-transpiler#89.

[stefanpenner]

i think the API should change to:

registry.add('htmlbars-ast-plugin', {
  name: 're-write-stuff',
  plugin: { name: 're-write-stuff', relativeTo: __dirname }
});

Which enables the underlying plugin to handle the "im developing my add-on" or "my addon dep changed" cases.

[rwjblue]

Was addressed by #90.