Bump version (fake) to match updated crate number

Change-Id: I8cf1975eae76c99ef98b5edba5dc84cebefe80b4
diff --git a/Cargo.toml b/Cargo.toml
index 083b10d..354a84a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 
 name          = "mio"
-version       = "0.6.11"
+version       = "0.6.12"
 license       = "MIT"
 authors       = ["Carl Lerche <me@carllerche.com>"]
 description   = "Lightweight non-blocking IO"