Bumped version to 0.5.1 (#174)

* Updated a dependency

* Bumped version to 0.5.1

Author: elichai

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "web3"
-version = "0.5.0"
+version = "0.5.1"
 description = "Ethereum JSON-RPC client."
 homepage = "https://github.com/tomusdrw/rust-web3"
 repository = "https://github.com/tomusdrw/rust-web3"
@@ -18,7 +18,7 @@ ethereum-types = "0.4"
 futures = "0.1"
 jsonrpc-core = "8.0.1"
 log = "0.4"
-parking_lot = "0.5"
+parking_lot = "0.7"
 rustc-hex = "1.0"
 serde = "1.0"
 serde_derive = "1.0"