Fix analysis issues.

Author: nex3

benchmark/generate.dart

@@ -28,7 +28,7 @@ main() async {
       footer: '.bar {@extend .foo}');
 }
 
-Future writeNTimes(String path, String text, int times,
+Future writeNTimes(String path, String text, num times,
     {String header, String footer}) async {
   print("Generating $path...");
   var file = new File(path).openWrite();

lib/src/render.dart

@@ -5,7 +5,6 @@
 import 'package:path/path.dart' as p;
 
 import 'ast/sass.dart';
-import 'exception.dart';
 import 'io.dart';
 import 'sync_package_resolver.dart';
 import 'visitor/perform.dart';

tool/grind.dart

@@ -71,7 +71,8 @@ js() {
 @Task('Build a pure-JS npm package.')
 @Depends(js)
 npm_package() {
-  var json = JSON.decode(new File('package/package.json').readAsStringSync());
+  var json = JSON.decode(new File('package/package.json').readAsStringSync())
+      as Map<String, dynamic>;
   json['version'] = _version;
 
   _writeNpmPackage('build/npm', json);