cargo: separate public and private dependencies

Cargo.toml

@@ -13,16 +13,17 @@ keywords = ["gitlab", "api"]
 categories = ["web-programming", "api-bindings"]
 
 [dependencies]
-chrono = { version = "~0.3", features = ["serde"] }
-error-chain = "~0.9"
 hyper = { version = "~0.10", default-features = false }
 itertools = "~0.5"
 log = "~0.3"
 reqwest = "~0.4"
-serde = "~0.9"
 serde_derive = "~0.9"
-serde_json = "~0.9"
 url = "^1.4"
 
+chrono = { version = "~0.3", features = ["serde"] }
+error-chain = "~0.9"
+serde = "~0.9"
+serde_json = "~0.9"
+
 [features]
 strict = []