Refactor JavaScript library.

- Separate classes in separate modules (files)
- Constants should be associated with a class
- Replace exports.config scheme with a config singleton
- Refactor base58 functions as a static class

test/offer-test.js

@@ -9,8 +9,8 @@ var Server      = require("./server").Server;
 
 var testutils = require("./testutils");
 
-require("../src/js/amount").config = require("./config");
-require("../src/js/remote").config = require("./config");
+var extend      = require('extend');
+extend(require('../src/js/config'), require('./config'));
 
 buster.testRunner.timeout = 5000;