delegate options to transform call

[magalhas]

As the title says. The options parameter just takes the harmony flag for now, but it may take other options in the future. I'm going to open a PR for this.

[wincent]

Looks useful.

[magalhas]

This is in fact already merged. Going to close this.

[wincent]

Yep, I noticed this after by looking at the commit history.

In case you think it's worth mentioning in the docs, here's a PR that updates them: #29