Update tests to support latest ripple-lib:

* Update ripple-lib api usage
* Use latest npm ripple-lib
  * Tested with bignumber.js branch and tip of develop
* Use new version of coffee-script
  * Better source maps
* Update mocha
* Add assert-diff for better error reporting
* Add rconsole, enabled via USE_RCONSOLE env var
  * For use with manual installation only

test/mocha-loader-patch.js

@@ -2,6 +2,11 @@ mocha = require("mocha")
 // Stash a reference away to this
 old_loader = mocha.prototype.loadFiles
 
+// Optionally use a more useful (but noisy) logger
+if (process.env.USE_RCONSOLE) {
+  require('rconsole');
+};
+
 if (!old_loader.monkey_patched) {
   // Gee thanks Mocha ...
   mocha.prototype.loadFiles = function() {