Add support for deflate and gzip compression

[oderayi]

closes: https://github.com/simonh1000/angular-http-server/issues/26

This change is to add compression (gzip and deflate) support for content ['application/javascript', 'application/json', 'text/html', 'text/css'] automatically (without a command line switch) based on the Accept-Encoding request header entry.

Didn't have much time to write the tests but, my instinct tells me it works. Might need a bit of optimization here and there.

[simonh1000]

@oderayi can you provide some answers so that I can merge?