Fix error_def version

In case it breaks in future versions

Author: kc1212

Diff for: Cargo.toml

@@ -13,7 +13,7 @@ keywords = ["gnunet", "gns", "p2p"]
 unix_socket = ">= 0.5"
 rand = ">= 0.3"
 byteorder = ">= 0.5"
-error_def = ">= 0.3.10"
+error_def = "== 0.3.10"
 rust-crypto = ">= 0.2.36"
 num = ">= 0.1.24"
 regex = ">= 0.1.71"