no longer require entry points to be specified in the build.dart file

pkg/polymer/lib/transformer.dart

Index: pkg/polymer/lib/transformer.dart
diff --git a/pkg/polymer/lib/transformer.dart b/pkg/polymer/lib/transformer.dart
index 997357ad4a11ede20962f46337d22b333080a626..c367716ec5dbd410f46cecb93ab5c00279a7eea3 100644
--- a/pkg/polymer/lib/transformer.dart
+++ b/pkg/polymer/lib/transformer.dart
@@ -45,7 +45,7 @@ TransformOptions _parseSettings(BarbackSettings settings) {
   bool injectBuildLogs =
       !releaseMode && args['inject_build_logs_in_output'] != false;
   return new TransformOptions(
-      entryPoints: _readEntrypoints(args['entry_points']),
+      entryPoints: readEntrypoints(args['entry_points']),
       inlineStylesheets: _readInlineStylesheets(args['inline_stylesheets']),
       directlyIncludeJS: jsOption == null ? releaseMode : jsOption,
       contentSecurityPolicy: csp,
@@ -54,7 +54,7 @@ TransformOptions _parseSettings(BarbackSettings settings) {
       injectBuildLogsInOutput: injectBuildLogs);
 }
 
-_readEntrypoints(value) {
+readEntrypoints(value) {
   if (value == null) return null;
   var entryPoints = [];
   bool error;