feat/ Send requests to server, minor refactoring

@phoenix16t @armandopmj
* I wrote a lot of GET and POST requests to the server (code found in /client/www/js/services.js). Please take a look at them and let me know what you think.
* I'm not sure what URL I should be sending the requests to. Also, what would the URL be after deploying the app? (issue #32)
* We need to start working on authentication. (issue #29)