Allow multiple reporters

[shaicantor]

Can you add the feature to add multiple reporters?
For example: spec and xunit.
Meaning, writing spec output and xunit xml file.
There are a few reporters that are doing this, but the tap-mocha-reporter used by tap doesn't allow it.

https://www.npmjs.com/package/spec-xunit-file
https://www.npmjs.com/package/tap-xunit-file