Refactor to use renderChunk instead of removed transformBundle

[Andarist]

fixes #210

[mjeanroy]

Hi @Andarist,

Thanks for your PR (and sorry for the delay, but I was on vacation).

My original plan was to keep compatibility with old versions of rollup (basically < 0.66, not so hard to do by the way), with a warning log and remove this support when I'll release a 1.0.0 version (and since rollup just released a stable 1.0.0 version, I plan to to do it very soon).

But I would be happy to have your opinion about this? Do you think support of old versions of rollup should be removed now?

[Andarist]

Well, i don't know how to detect reliably which version of rollup is used - so not sure how to keep the backwards compatibility.

IMHO with rollup having fairly stable API and having this hook for quire some time before v1 release, I'd say it's not worth much to keep the compatibility anyway - personally I'm in favour of moving faster as rollup updates are really quite easy to do. If somebody is still on older version they can just install compatible version of rollup-plugin-prettier