Boot genesis block helper

Before this change, if you wanted to use a new Transaction
feature in the genesis block, you'd need to extend its
Creator object and associated methods.  With yesterday's
addtions to Transcation, it's now so easy to work with
Transactions directly that we can get rid of the middleman.

Also added a KeyPair type alias, so that ring could be easily swapped
out with a competing library, if needed.

src/accountant_stub.rs

@@ -6,10 +6,9 @@ use std::net::UdpSocket;
 use std::io;
 use bincode::{deserialize, serialize};
 use transaction::Transaction;
-use signature::{PublicKey, Signature};
+use signature::{KeyPair, PublicKey, Signature};
 use hash::Hash;
 use entry::Entry;
-use ring::signature::Ed25519KeyPair;
 use accountant_skel::{Request, Response};
 
 pub struct AccountantStub {
@@ -36,7 +35,7 @@ impl AccountantStub {
     pub fn transfer(
         &self,
         n: i64,
-        keypair: &Ed25519KeyPair,
+        keypair: &KeyPair,
         to: PublicKey,
         last_id: &Hash,
     ) -> io::Result<Signature> {
@@ -116,16 +115,16 @@ mod tests {
     use accountant_skel::AccountantSkel;
     use std::thread::{sleep, spawn};
     use std::time::Duration;
-    use genesis::{Creator, Genesis};
+    use genesis::Genesis;
+    use signature::{generate_keypair, get_pubkey};
 
     #[test]
     fn test_accountant_stub() {
         let addr = "127.0.0.1:9000";
         let send_addr = "127.0.0.1:9001";
-        let bob = Creator::new(1_000);
-        let bob_pubkey = bob.pubkey;
-        let alice = Genesis::new(10_000, vec![bob]);
+        let alice = Genesis::new(10_000);
         let acc = Accountant::new(&alice, None);
+        let bob_pubkey = get_pubkey(&generate_keypair());
         spawn(move || AccountantSkel::new(acc).serve(addr).unwrap());
         sleep(Duration::from_millis(30));
 
@@ -135,6 +134,6 @@ mod tests {
         let sig = acc.transfer(500, &alice.get_keypair(), bob_pubkey, &last_id)
             .unwrap();
         acc.wait_on_signature(&sig).unwrap();
-        assert_eq!(acc.get_balance(&bob_pubkey).unwrap().unwrap(), 1_500);
+        assert_eq!(acc.get_balance(&bob_pubkey).unwrap().unwrap(), 500);
     }
 }