Make Aphlict client somewhat more approachable

Summary: Provide a reasonable JS API for the Aphlict client. Provide an example behavior to invoke it.

Test Plan:
Ran "aphlict_server.js" with:

$ sudo node aphlict_server.js

Loaded /aphlict/. Opened console. Got "hello" from the server every second.

Got reasonable errors with the server not present ("Security exception", but this is because it can't connect to port 843 to access the policy server).

Reviewers: ddfisher, keebuhm, allenjohnashton, btrahan

Reviewed By: btrahan

CC: aran, epriestley

Maniphest Tasks: T944

Differential Revision: https://secure.phabricator.com/D1800