Remove toolbar config merge

Previous to this release, your custom toolbar config would have been merged together with the default toolbar config, which made it difficult to remove default toolbar elements.

With this release, the following config will now produce a toolbar with exactly what it says on the tin (Bold, orderedList, unorderedList)

editorConfig: {
  modules: {
    toolbar: [
      ['bold'],
      [
        { 'list': 'ordered' }, { 'list': 'bullet' }
      ]
    ]
  },
  theme: 'snow'
}