easy to use conversion from and to string for ethstore::Crypto (#5437)

* easy to use conversion from and to string for ethstore::Crypto

* ethstore uses tempdir instead of devtools

* ethstore does not depend on ethcore-util

ethcrypto/src/lib.rs

@@ -94,11 +94,11 @@ pub trait Keccak256<T> {
 	fn keccak256(&self) -> T where T: Sized;
 }
 
-impl Keccak256<[u8; 32]> for [u8] {
+impl<T> Keccak256<[u8; 32]> for T where T: AsRef<[u8]> {
 	fn keccak256(&self) -> [u8; 32] {
 		let mut keccak = Keccak::new_keccak256();
 		let mut result = [0u8; 32];
-		keccak.update(self);
+		keccak.update(self.as_ref());
 		keccak.finalize(&mut result);
 		result
 	}