Adds a std::default::Default implementation for ValidatorRecord

Updates the test generation so that it uses sane values for some marker values
like `FAR_FUTURE_SLOT`

beacon_chain/utils/bls/src/public_key.rs

@@ -1,6 +1,7 @@
 use super::SecretKey;
 use bls_aggregates::PublicKey as RawPublicKey;
 use ssz::{decode_ssz_list, Decodable, DecodeError, Encodable, SszStream};
+use std::default;
 
 /// A single BLS signature.
 ///
@@ -20,6 +21,13 @@ impl PublicKey {
     }
 }
 
+impl default::Default for PublicKey {
+    fn default() -> Self {
+        let secret_key = SecretKey::random();
+        PublicKey::from_secret_key(&secret_key)
+    }
+}
+
 impl Encodable for PublicKey {
     fn ssz_append(&self, s: &mut SszStream) {
         s.append_vec(&self.0.as_bytes());