support for --address param

[kdabir]

https://developers.google.com/appengine/docs/java/tools/devserver -

--address=...
The host address to use for the server. You may need to set this to be able to access the development server from another computer on your network. An address of 0.0.0.0 allows both localhost access and hostname access. Default is localhost.

Currently gae closure does not support this configuration value.

I have implemented it and am submitting a pull request. Please review and accept.

I think issue #46 is also related. I am just creating an new issue because am not sure if --host is meant for the same.

[bmuschko]

Fixed with your pull request #52.