Add readme section to Cargo.toml
diff --git a/Cargo.toml b/Cargo.toml
index a693e87..6047243 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -10,6 +10,7 @@
 description = "Task abstraction for building executors"
 keywords = ["futures", "task", "executor", "spawn"]
 categories = ["asynchronous", "concurrency"]
+readme = "README.md"
 
 [dependencies]
 crossbeam-utils = "0.6.5"