Add time crate

Cargo.toml

@@ -16,4 +16,5 @@ git = "https://github.com/apoelstra/bitcoin-secp256k1-rs.git"
 
 [dependencies]
 rustc-serialize = "*"
+time = "*"
 

src/lib.rs

@@ -47,6 +47,7 @@ extern crate core;
 extern crate rand;
 extern crate rustc_serialize as serialize;
 extern crate test;
+extern crate time;
 
 extern crate secp256k1;
 extern crate crypto;