Add support for custom source file extensions

[orta]

I'd like to be able to support TypeScript today, but this feature could mean the special-casing of coffeescript support could be removed as there's enough here to allow anyone to add that support in their own apps easily.

[Igmat]

I'm not sure that it would be enough for additional type of transpilers, but it's a good start.
I tried to achieve TS support inside vm by calling pirates inside NodeVM but it seems that require and module can't be affected by script code.

[orta]

Good call, I did end up using this in danger-js, but I think moving to pirates is probably what I want to do in the future, thanks!

[orta]

Merging, it's been used in danger in prod for the best part of a year

[hmagrini]

@orta could you restore the custom_files branch? it seems that DangerJS is using that branch as dependency, thus all installations that depend on DangerJS seem to be failing to install.

[orta]

Heh, I have a tool that auto delete branches, that should keep it running 👍

[hmagrini]

awesome, thanks for the quick response!

[michaeljacobdavis]

@patriksimek Would it be possible to do a publish of vm2 that includes this?

[patriksimek]

@michaeljacobdavis I have just added @orta into npm maintainers. I'm temporarily unavailable to maintain the project. Thank you!

[orta]

Ace, thanks @patriksimek

[orta]

Hah, sorry about all ^ 🍡