refactor(build): simplify and modularize

simplify:
- use same html file for dart and JS
- build benchmarks automatically when doing `gulp build`
- centralize configuration

modularize:
- move all build tasks into separate node.js modules under
  `tools/build`.

changes:
- the `build` folder is now the `dist` folder

Closes #284

modules/benchpress/pubspec.yaml

@@ -0,0 +1,4 @@
+name: benchpress
+environment:
+  sdk: '>=1.4.0'
+dependencies:

modules/benchpress/src/benchpress.dart

@@ -0,0 +1,63 @@
+library benchmarks.benchpress;
+
+import 'dart:js' as js;
+import 'dart:html';
+import 'dart:async';
+
+// TODO: move the functionality of this module into benchpress and replace this
+// file with a Dart wrapper!
+
+var _benchmarkNames = [];
+
+_benchmarkId(index) {
+  return "benchmark${index}";
+}
+
+_useBenchmark(index) {
+  var search = window.location.search;
+  if (search.length > 0) {
+    search = search.substring(1);
+  }
+  if (search.length > 0) {
+    return search == _benchmarkId(index);
+  } else {
+    return true;
+  }
+}
+
+_onLoad(callback) {
+  var isReady = document.readyState == 'complete';
+  if (isReady) {
+    Timer.run(callback);
+  } else {
+    window.addEventListener('load', (event) => callback(), false);
+  }
+}
+
+_createBenchmarkMenu() {
+  var div = document.createElement('div');
+  div.innerHtml += '<h1>Benchmarks:</h1><a class="btn btn-default" href="?">All</a>';
+  for (var i=0; i<_benchmarkNames.length; i++) {
+    var activeClass = _useBenchmark(i) ? 'active' : '';
+    div.innerHtml += '<a class="btn btn-default ${activeClass}" href="?${_benchmarkId(i)}">${_benchmarkNames[i]}</a>';
+  }
+  document.body.insertBefore(div, document.body.childNodes[0]);
+}
+
+benchmark(name, stepsCreationCallback) {
+  _benchmarkNames.add(name);
+  if (_benchmarkNames.length == 2) {
+    _onLoad(_createBenchmarkMenu);
+  }
+  if (_useBenchmark(_benchmarkNames.length-1)) {
+    stepsCreationCallback();
+  }
+}
+
+benchmarkStep(name, callback) {
+  var benchmarkName = _benchmarkNames[_benchmarkNames.length-1];
+  js.context['benchmarkSteps'].add(new js.JsObject.jsify({
+      "name": benchmarkName + '#' + name,
+      "fn": new js.JsFunction.withThis((_) => callback())
+  }));
+}

modules/benchpress/src/benchpress.es6

@@ -0,0 +1,55 @@
+// TODO: move the functionality of this module into benchpress itself!
+
+var benchmarkNames = [];
+
+function benchmarkId(index) {
+  return 'benchmark' + index;
+}
+
+function useBenchmark(index) {
+  var search = window.location.search;
+  if (search.length > 0) {
+    search = search.substring(1);
+  }
+  if (search.length > 0) {
+    return search == benchmarkId(index);
+  } else {
+    return true;
+  }
+}
+
+function onLoad(callback) {
+  var isReady = document.readyState === 'complete';
+  if (isReady) {
+    window.setTimeout(callback);
+  } else {
+    window.addEventListener('load', callback, false);
+  }
+}
+
+function createBenchmarkMenu() {
+  var div = document.createElement('div');
+  div.innerHTML += '<h1>Benchmarks:</h1><a class="btn btn-default" href="?">All</a>';
+  for (var i=0; i<benchmarkNames.length; i++) {
+    var activeClass = useBenchmark(i) ? 'active' : '';
+    div.innerHTML += ('<a class="btn btn-default '+activeClass+'" href="?'+benchmarkId(i)+'">'+benchmarkNames[i]+'</a>');
+  }
+  document.body.insertBefore(div, document.body.childNodes[0]);
+}
+
+export function benchmark(name, stepsCreationCallback) {
+  benchmarkNames.push(name);
+  if (benchmarkNames.length === 2) {
+    onLoad(createBenchmarkMenu);
+  }
+  if (useBenchmark(benchmarkNames.length-1)) {
+    stepsCreationCallback();
+  }
+}
+
+export function benchmarkStep(name, callback) {
+  var benchmarkName = benchmarkNames[benchmarkNames.length-1];
+  window.benchmarkSteps.push({
+    name: benchmarkName + '#' + name, fn: callback
+  });
+}