Convert to ES5, add web server

* No compilation step
 * Beginnings of web interface
 * Simple express server; React-based frontend
 * CommonJS style across codebase; auto-converts to RequireJS for browser
 * Using diffsync for realtime UI
 * "Provider" -> "Plugin"
 * Plugins expose one or more Providers

lib/util/autoamd.js

@@ -0,0 +1,30 @@
+var interceptor = require('express-interceptor');
+
+/**
+ * Express middleware that converts CommonJS-style code to RequireJS style for the browser (assuming require.js is loaded).
+ */
+
+module.exports = function(urlPrefix) {
+  return interceptor(function(req, res){
+    return {
+      // Only URLs with the given prefix will be converted to require.js style
+      isInterceptable: function(){
+        return req.originalUrl.indexOf(urlPrefix) == 0;
+      },
+      intercept: function(body, send) {
+        send(toRequireJS(body));
+      }
+    };
+  });
+}
+
+// From https://github.com/shovon/connect-commonjs-amd/blob/master/src/middleware.coffee
+function toRequireJS(str) {
+  var requireCalls = str.match(/require\((\s+)?('[^'\\]*(?:\\.[^'\\]*)*'|"[^"\\]*(?:\\.[^"\\]*)*")(\s+)?\)/g) || [];
+  requireCalls = requireCalls.map(function(str) {
+    return (str.match(/('[^'\\]*(?:\\.[^'\\]*)*'|"[^"\\]*(?:\\.[^"\\]*)*")/))[0];
+  });
+  requireCalls.unshift("'require'");
+  str = "define([" + (requireCalls.join(', ')) + "], function (require) {\nvar module = { exports: {} }\n  , exports = module.exports;\n\n(function () {\n\n" + str + "\n\n})();\n\nreturn module.exports;\n});";
+  return str;
+};