- Notes:
        Add instrument command support for the 'cwd' option
        Refactor nyc-integration instrument tests so tests with output folder specified aren't in the no output folder suite
        Refactor instrument.js and instrumentAllFiles command to use modern javascript
        Remove call to deprecated 'process.exit()' in instrument command
        Use file extension as an index to find the correct transform, rather than trying to match a transform name to the rightmost characters of a filename
            * There is another one of these in the code base but it's out of the scope of this PR
        BTW, I'm not going to widen the scope of this PR, this is it!
     - Assumptions:
        If you're instrumenting a single file cwd/a/b/d.js, and specifying an output directory cwd/e, the result will be cwd/e/d.js
        That we want to use file extensions for find transforms, the existing implementation would use the '.js' instrumenter for both '.js' and '.mjs' files, these changes assume that was wrong.
	That the filename in the covered file should be of the form './path/to/file.js'

This is intended to sit on top of the nyc es2015+ commit.  It uses the cwd option and its defaults in nyc to make paths more consistent.

All changed, so all this does now is propagate `cwd` so that it can influence `testExclude` and `require` path settings.