bigint upgraded to version 3.0 (#5986)

* bigint upgraded to version 3.0

* fixed missing FromHex import in ethcore tests

* fixed missing FromHex import in rpc tests

ethkey/cli/Cargo.toml

@@ -5,7 +5,7 @@ authors = ["Parity Technologies <admin@parity.io>"]
 
 [dependencies]
 ethkey = { path = "../" }
-rustc-serialize = "0.3"
+rustc-hex = "1.0"
 docopt = "0.7"
 
 [[bin]]

ethkey/cli/src/main.rs

@@ -15,13 +15,13 @@
 // along with Parity.  If not, see <http://www.gnu.org/licenses/>.
 
 extern crate docopt;
-extern crate rustc_serialize;
+extern crate rustc_hex;
 extern crate ethkey;
 
 use std::{env, fmt, process};
 use std::num::ParseIntError;
 use docopt::Docopt;
-use rustc_serialize::hex::{FromHex, FromHexError};
+use rustc_hex::{FromHex, FromHexError};
 use ethkey::{KeyPair, Random, Brain, Prefix, Error as EthkeyError, Generator, sign, verify_public, verify_address};
 
 pub const USAGE: &'static str = r#"