Parameterize uri resolution and parsing of options, use package:path

test/indenting_writer_test.dart

 #!/usr/bin/env dart
 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library indenting_writer_test;
 
-import 'package:protoc-plugin/protoc.dart';
+import 'package:protoc_plugin/protoc.dart';
 import 'package:unittest/unittest.dart';
 
 void main() {
   test('testIndentingWriter', () {
     String blockExpected = r'''class test{
   body;
 }
 ''';
 
     var iob = new MemoryWriter();
     var writer = new IndentingWriter('  ', iob);
     writer.addBlock('class test{', '}', () {
       writer.println('body;');
     });
     expect(iob.toString(), blockExpected);
   });
 }