fix(build): correctly compile source files against typings

It looks like previously we were grabbing typings from outside of the tmp/ directory.
If this ever worked, it worked only by accident.

Author: IgorMinar

lib/broccoli/angular2-app.js

@@ -18,7 +18,17 @@ function Angular2App(defaults, options, additionalPaths) {
 }
 
 Angular2App.prototype.toTree = function() {
-    var sourceTree = 'src';
+    var sourceDir = 'src';
+
+    var sourceTree = new Funnel('src', {
+      destDir: 'src'
+    });
+
+    var typingsTree = new Funnel('typings', {
+      include: ['browser.d.ts', 'browser/**'],
+      destDir: 'typings'
+    });
+
     var vendorNpmFiles = [
       'systemjs/dist/system-polyfills.js',
       'systemjs/dist/system.src.js',
@@ -31,28 +41,36 @@ Angular2App.prototype.toTree = function() {
       'angular2/bundles/upgrade.dev.js'
     ];
 
+
+
     if (this.options && this.options.vendorNpmFiles) {
       vendorNpmFiles = vendorNpmFiles.concat(this.options.vendorNpmFiles);
     }
 
     var tsConfigCompilerOptions = JSON.parse(fs.readFileSync('src/tsconfig.json', 'utf-8')).compilerOptions;
+    // TODO(i): kill rootFilePaths in broccoli-typescript and use tsconfig.json#files instead
+    tsConfigCompilerOptions.rootFilePaths = JSON.parse(fs.readFileSync('src/tsconfig.json', 'utf-8')).files;
+
     tsConfigCompilerOptions.rootFilePaths = ['typings.d.ts'].concat(this.additionalPaths)
       .map(function(name) {
-        return path.join(process.cwd(), sourceTree, name)
+        return path.join(process.cwd(), sourceDir, name)
       });
 
-    var tsTree = compileWithTypescript(sourceTree, tsConfigCompilerOptions);
-    var tsSrcTree = new Funnel(sourceTree, {
+    var srcAndTypingsTree = mergeTrees([sourceDir, typingsTree]);
+
+    var tsTree = compileWithTypescript(srcAndTypingsTree, tsConfigCompilerOptions);
+
+    var tsSrcTree = new Funnel(sourceDir, {
       include: ['**/*.ts'],
       allowEmpty: true
     });
 
-    var jsTree = new Funnel(sourceTree, {
+    var jsTree = new Funnel(sourceDir, {
         include: ['**/*.js'],
         allowEmpty: true
     });
 
-    var assetTree = new Funnel(sourceTree, {
+    var assetTree = new Funnel(sourceDir, {
         include: ['**/*.*'],
         exclude: ['**/*.ts', '**/*.js'],
         allowEmpty: true