Remove upper case constants (#17)

Remove usage of upper-case constants.

Update SDK version.
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1e3f9a1..86c3777 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+# 0.9.6+1
+
+- Stop using deprecated constants from the SDK.
+
 # 0.9.6
 
 * Updates to support Dart 2.0 core library changes (wave
diff --git a/lib/src/bound_multipart_stream.dart b/lib/src/bound_multipart_stream.dart
index aab7ddd..e843727 100644
--- a/lib/src/bound_multipart_stream.dart
+++ b/lib/src/bound_multipart_stream.dart
@@ -304,8 +304,8 @@
           if (byte == CharCode.SP || byte == CharCode.HT) {
             _state = _HEADER_VALUE_START;
           } else {
-            String headerField = UTF8.decode(_headerField);
-            String headerValue = UTF8.decode(_headerValue);
+            String headerField = utf8.decode(_headerField);
+            String headerValue = utf8.decode(_headerValue);
             _headers[headerField.toLowerCase()] = headerValue;
             _headerField.clear();
             _headerValue.clear();
diff --git a/pubspec.yaml b/pubspec.yaml
index 1811771..e1fe578 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: mime
-version: 0.9.6
+version: 0.9.6+1
 author: Dart Team <misc@dartlang.org>
 description: Helper-package for working with MIME.
 homepage: https://www.github.com/dart-lang/mime