chore(dependencies): update to want 0.3

Author: seanmonstar

Cargo.toml

@@ -44,7 +44,7 @@ tokio-io = "0.2.0-alpha.2"
 tokio-sync = "0.2.0-alpha.2"
 tokio-net = { version = "0.2.0-alpha.2", optional = true, features = ["tcp"] }
 tokio-timer = { version = "0.3.0-alpha.2", optional = true }
-want = { git = "https://github.com/seanmonstar/want", branch = "std-future" }
+want = "0.3"
 
 [dev-dependencies]
 matches = "0.1"