Move Sapling verification checks into zcash_proofs crate

zcash_proofs/src/lib.rs

@@ -1,7 +1,5 @@
-#[cfg(test)]
-mod tests {
-    #[test]
-    fn it_works() {
-        assert_eq!(2 + 2, 4);
-    }
-}
+extern crate bellman;
+extern crate pairing;
+extern crate sapling_crypto;
+
+pub mod sapling;