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

lib/src/options.dart

Index: lib/src/options.dart
diff --git a/lib/src/options.dart b/lib/src/options.dart
index da65115e0f2a935ed212790d5d4da6a4573258e8..b99dd019a691a046fb298ed7189bf81874141fe9 100644
--- a/lib/src/options.dart
+++ b/lib/src/options.dart
@@ -311,8 +311,7 @@ final ArgParser argParser = StrongModeOptions.addArguments(new ArgParser()
 /// 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);