Boot futures 0.1

We added them thinking it'd be a good stepping stone towards an
asynchronous thin client, but it's used inconsistently and where
it used, the function is still synchronous, which is just confusing.

src/lib.rs

@@ -50,8 +50,6 @@ extern crate serde_json;
 extern crate sha2;
 extern crate untrusted;
 
-extern crate futures;
-
 #[cfg(test)]
 #[macro_use]
 extern crate matches;