feat(node-pty): option to stop handling SIGINT

[aslushnikov]

Fixes #190.

[msftclas]

All CLA requirements met.

[aslushnikov]

Hi guys,

In many node.js projects that deal with SIGINT/SIGTERM handling, there's an option to disable process signal hooks. This way it's up to the embedder to handle signals and to properly run shutdown logic.

This PR adds the handleSIGINT option to the pty.fork. AFAICT it'll fix the #190 bug - let me know what you think.

Thanks,
Andrey

[jerch]

@aslushnikov Care to test if #218 solves your issues with this?

[Tyriar]

This should be fixed with #218 which was just merged. Thanks for the PR though.