spawn istanbul in such a way that works for [email protected]

[bcoe]

@rmg pointed out in this pull request #30 that istanbul was being invoked in a manner that would work poorly if istanbul got hoisted up into a higher folder.

I've switched to using an approach which @othiym23 and @iarna suggested today:

1. I aded istanbul to npm run scripts.
2. I muck with the cwd, so that I can invoke the npm run script from the context of nyc.
3. I invoke the npm run script.

@jasisk I also added the statements option in this pull we didn't actually collide on the s key, because s was used on the outer yargs chain, not the inner yargs chain.

Let me know what ya'll think.

[rmg]

I was thinking more like just replacing the resolve with something like this:

require.resolve('istanbul/lib/cli');

[bcoe]

@rmg that's clever, I like that it wouldn't require calling chdir.

[jasisk]

👍. Sorry for the oversight on my part.