Improves how to initialize polymer apps and fixes polymer build and linter to

pkg/polymer/lib/builder.dart

Index: pkg/polymer/lib/builder.dart
diff --git a/pkg/polymer/lib/builder.dart b/pkg/polymer/lib/builder.dart
index 590155a46395db93758c40fb3e81d4e374f5f145..0e2b0b2d814208abca797396aa9bbbc9cdf5441c 100644
--- a/pkg/polymer/lib/builder.dart
+++ b/pkg/polymer/lib/builder.dart
@@ -279,12 +279,24 @@ CommandLineOptions parseOptions([List<String> args]) {
         defaultsTo: 'out')
     ..addFlag('help', abbr: 'h',
         negatable: false, help: 'Displays this help and exit.');
-  var res = parser.parse(args == null ? new Options().arguments : args);
-  if (res['help']) {
-    print('A build script that invokes the polymer linter and deploy tools.');
+
+  showUsage() {
     print('Usage: dart build.dart [options]');
     print('\nThese are valid options expected by build.dart:');
     print(parser.getUsage());
+  }
+
+  var res;
+  try {
+    res = parser.parse(args == null ? new Options().arguments : args);
+  } on FormatException catch (e) {
+    print(e.message);
+    showUsage();
+    exit(1);
+  }
+  if (res['help']) {
+    print('A build script that invokes the polymer linter and deploy tools.');
+    showUsage();
     exit(0);
   }
   return new CommandLineOptions(res['changed'], res['removed'], res['clean'],