Fix typo in README

O_TRUNC was listed twice, and O_CREATE omitted from the release notes.

README.md

diff --git a/README.md b/README.md
index 36f52f6..3e498ea 100644
--- a/README.md
+++ b/README.md
@@ -168,7 +168,7 @@
 ## Release Notes
 * **0.9.0** 2015.11.05
   * New Walk function similar to filepath.Walk
-  * MemMapFs.OpenFile handles O_TRUNC, O_APPEND, O_TRUNC
+  * MemMapFs.OpenFile handles O_CREATE, O_APPEND, O_TRUNC
   * MemMapFs.Remove now really deletes the file
   * InMemoryFile.Readdir and Readdirnames work correctly
   * InMemoryFile functions lock it for concurrent access