Support binary mode for HTTP responses

[garie]

Mountebank 1.10.0 supports binary responses: http://www.mbtest.org/docs/protocols/http

[miccheng]

@garie So i have merged the 2 branches you referenced. Look forward to your new pull request. 🙇

[garie]

Thanks! It is definitely working in that it's setting the mode correctly on the mountebank responses, but I haven't actually got it working yet with binary data and I'm not sure why. I posted in the google group for mountebank (https://groups.google.com/forum/#!topic/mountebank-discuss/GpM80zBk86o) and will probably put in a PR as soon as I can figure out what I'm doing wrong.