Update tokio to 0.3 (#38)

Author: taiki-e

async-stream-impl/Cargo.toml

@@ -21,4 +21,4 @@ quote = "1"
 async-stream = { version = "0.3.0", path = "../async-stream" }
 futures-core = "0.3"
 futures-util = "0.3"
-tokio = { version = "0.2", features = ["full"] }
+tokio = { version = "0.3", features = ["full"] }

async-stream/Cargo.toml

@@ -25,6 +25,6 @@ futures-core = "0.3"
 
 [dev-dependencies]
 futures-util = "0.3"
-tokio = { version = "0.2", features = ["full"] }
-tokio-test = "0.2"
+tokio = { version = "0.3", features = ["full"] }
+tokio-test = "0.3"
 trybuild = "1"