fixed slice to use end index rather than length (#62)

diff --git a/lib/src/encoding_parser.dart b/lib/src/encoding_parser.dart
index d97e4cc..ef5e708 100644
--- a/lib/src/encoding_parser.dart
+++ b/lib/src/encoding_parser.dart
@@ -117,7 +117,7 @@
   String slice(int start, [int end]) {
     if (end == null) end = length;
     if (end < 0) end += length;
-    return _bytes.substring(start, end - start);
+    return _bytes.substring(start, end);
   }
 }
 
diff --git a/test/parser_feature_test.dart b/test/parser_feature_test.dart
index e5c1d8c..de8843b 100644
--- a/test/parser_feature_test.dart
+++ b/test/parser_feature_test.dart
@@ -335,6 +335,13 @@
     test('ignores whitespace', () {
       expect(getEncoding('  <meta charset="utf-16">'), 'utf-16');
     });
+
+    test('parses content attr', () {
+      expect(
+          getEncoding(
+              '<meta http-equiv="content-type" content="text/html; charset=UTF-8">'),
+          null);
+    });
   });
 }