Update to uuid 0.7 (#340)

Cargo.toml

@@ -31,7 +31,7 @@ serde_urlencoded = "0.5"
 tokio = "0.1.7"
 tokio-io = "0.1"
 url = "1.2"
-uuid = { version = "0.6", features = ["v4"] }
+uuid = { version = "0.7", features = ["v4"] }
 
 [dev-dependencies]
 env_logger = "0.5"

src/multipart.rs

@@ -23,7 +23,7 @@ impl Form {
     /// Creates a new Form without any content.
     pub fn new() -> Form {
         Form {
-            boundary: format!("{}", Uuid::new_v4().simple()),
+            boundary: format!("{}", Uuid::new_v4().to_simple()),
             fields: Vec::new(),
             headers: Vec::new(),
         }