Decorators on computed class method names

[leonid-bauxy]

I propose that support for decorators on computed properties is added to babylon.

It was suggested in babel-eslint repo, that I open an issue here.
Related issue: babel/babel-eslint#309.

This doesn't work right now:

  @autobind
  [method](arg) {
      // do something
  }

[hzoo]

This is handled by #587 and will be in the next beta release which should be 7.0.0-beta.15 (soon)