Revert "Merge pull request #200 from sigp/new-structure"

This reverts commit d7a3545be1, reversing
changes made to 1da06c156c.

eth2/utils/bls/src/keypair.rs

@@ -0,0 +1,16 @@
+use super::{PublicKey, SecretKey};
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Keypair {
+    pub sk: SecretKey,
+    pub pk: PublicKey,
+}
+
+impl Keypair {
+    /// Instantiate a Keypair using SecretKey::random().
+    pub fn random() -> Self {
+        let sk = SecretKey::random();
+        let pk = PublicKey::from_secret_key(&sk);
+        Keypair { sk, pk }
+    }
+}