Bump version to 1.1.1 (#7)

diff --git a/pubspec.yaml b/pubspec.yaml
index ad38383..74f5564 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: platform
-version: 1.1.0
+version: 1.1.1
 authors:
 - Todd Volkert <tvolkert@google.com>
 description: A pluggable, mockable platform abstraction for Dart.