Add multipart/form-data support

Cargo.toml

@@ -16,6 +16,7 @@ hyper = "0.11"
 hyper-tls = "0.1.2"
 libflate = "0.1.11"
 log = "0.3"
+mime_guess = "2.0.0-alpha.2"
 native-tls = "0.1.3"
 serde = "1.0"
 serde_json = "1.0"
@@ -24,11 +25,12 @@ tokio-core = "0.1.6"
 tokio-io = "0.1"
 tokio-tls = "0.1"
 url = "1.2"
+uuid = { version = "0.5", features = ["v4"] }
 
 [dev-dependencies]
 env_logger = "0.4"
-serde_derive = "1.0"
 error-chain = "0.10"
+serde_derive = "1.0"
 
 [features]
 unstable = []