cargo: pin the version of the log crate

Cargo.toml

@@ -18,7 +18,7 @@ serde_codegen = "~0.8"
 chrono = { version = "~0.2", features = ["serde"] }
 ease = "~0.6"
 hyper = "~0.9"
-log = "*"
+log = "~0.3"
 quick-error = "~1.1"
 serde = "~0.8"
 serde_json = "~0.8"