fix(cargo): Bump dependencies so that Tokio compiles with minimal versions (#258)

tokio-io/Cargo.toml

@@ -17,6 +17,6 @@ Core I/O primitives for asynchronous I/O in Rust.
 categories = ["asynchronous"]
 
 [dependencies]
-bytes = "0.4"
+bytes = "0.4.1"
 futures = "0.1.18"
 log = "0.4"

tokio-threadpool/Cargo.toml

@@ -18,7 +18,7 @@ futures = "0.1.19"
 crossbeam-deque = "0.3"
 num_cpus = "1.2"
 rand = "0.4"
-log = "0.3"
+log = "0.4"
 
 # Futures 0.2 integration
 futures2 = { version = "0.1", path = "../futures2", optional = true }