Bump version

Change-Id: I14771f09d09b442b4e6383e56f99a218cfd015c6
diff --git a/Cargo.toml b/Cargo.toml
index 354a84a..dd8e91b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 
 name          = "mio"
-version       = "0.6.12"
+version       = "0.6.13"
 license       = "MIT"
 authors       = ["Carl Lerche <me@carllerche.com>"]
 description   = "Lightweight non-blocking IO"