fixes #276, path manipulation issues on windows. Also fixes server mode

lib/src/options.dart

 // Copyright (c) 2014, 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.
 
 /// Set of flags and options passed to the compiler
 library dev_compiler.src.options;
 
 import 'dart:io';
 
 import 'package:args/args.dart';
@@ skipping 293 matching lines @@
       defaultsTo: 'iojs')
   ..addOption('dump-info-file',
       abbr: 'f',
       help: 'Dump info json file (requires dump-info)',
       defaultsTo: null));
 
 /// Tries to find the `lib/runtime/` directory of the dev_compiler package. This
 /// works when running devc from it's sources or from a snapshot that is
 /// activated via `pub global activate`.
 String _computeRuntimeDir() {
-  var scriptUri = Platform.script;
-  var scriptPath = scriptUri.path;
+  var scriptPath = path.fromUri(Platform.script);
   var file = path.basename(scriptPath);
   var dir = path.dirname(scriptPath);
   var lastdir = path.basename(dir);
   dir = path.dirname(dir);
 
   // Both the source devc.dart and the snapshot generated by pub global activate
   // are under a bin folder.
   if (lastdir != 'bin') return null;
 
   // And both under a project directory containing a pubspec.lock file.
@@ skipping 26 matching lines @@
     // The pub-cache directory is two levels up, but we verify that the layout
     // looks correct.
     if (path.basename(dir) != 'dev_compiler') return null;
     dir = path.dirname(dir);
     if (path.basename(dir) != 'global_packages') return null;
     dir = path.dirname(dir);
     return path.join(dir, cacheDir, 'lib', 'runtime');
   }
   return null;
 }