Checkpoint: Signing seems to work, but there's a lot of cruft and cross-checks.

src/lib.rs

@@ -24,6 +24,8 @@ extern crate sha1;
 extern crate sha2;
 #[macro_use]
 extern crate simple_asn1;
+#[cfg(test)]
+extern crate crypto;
 
 /// The `rsa` module provides bare-bones support for RSA signing, verification,
 /// encryption, decryption, and key generation.