Add easy API proxy ability

[eastridge]

Should use:

https://github.com/walmartlabs/mock-server

[eastridge]

@kenwheeler What we want to do here is have the generator prompt for a server to proxy. So for instance:

Specify an API server to proxy (example: search.twitter.com)?

Then walmartlabs/mock-server would be added as a dependency in the generated project, and we'd build out a config file like this:

https://github.com/kpdecker/mock-server-meetup/blob/master/mock-server.json

Get a demo of it working and we'll figure out how it should play with the default grunt command (i.e. start a connect server, or start a mock-server?)

If there is something simpler that does what mock-server does I'm open to it but would rather use WalmartLabs projects where possible.

[eastridge]

@kenwheeler I'm assigning this to @Trombom because I want your help on core.

[mulderp]

If it is just about the mock of JSON, maybe https://github.com/sideshowcoder/canned is interesting.