added support for regex in proxy options

[jamon]

provide configurations where the path is a regular expression, eg:

        proxy: [
            {
                path: /\/google(.*)/,
                target: "http://www.google.com/"
            }
        ],

[sokra]

This part should be moved into lib/Server.js to allow this config style without the CLI too.

[AprilArcus]

This would be super useful for us! We are working on a mock server that has to support a very heterogenous legacy route scheme, and we'd like to be able to white-list certain routes and proxy the rest.

[sokra]

@AprilArcus take a look at the note, fix it and create another PR.

[ntharim]

I fixed this in #187. Please a have look.

[PavelGavlik]

Shouldn't we close this PR when #187 has superseded this PR and it has been merged?