Additional config support

Hi,

I made some changes to allow passing additional config parameters to http-proxy.
You can now do things like the following to proxy https services:
````
proxy: {
    proxy1: {
        options: {
            host: 'localhost',
            port: 9000,

            https: {
                key: fs.readFileSync( path.join(proxyKeysDir, 'server.key'), 'utf8' ),
                cert: fs.readFileSync( path.join(proxyKeysDir, 'server.crt'), 'utf8' )
            },
            changeOrigin: true
            router: {
                'localhost/secure': 'https://mysecure.server.com:443/subpath',
                'localhost/insecure/': 'http://127.0.0.1:3000'
            }
        }
    }
}
```
I also added a default port of 9000, changed over to grunt-mocha-test to avoid the warning message and added tests for all the changes.