added the openssl-sys to the cargo.toml

Cargo.toml

@@ -14,3 +14,10 @@ lettre = { version = "0.10.0-rc.4", features = [
   "smtp-transport",
   "native-tls",
 ] }
+openssl-sys = "*"
+
+[features]
+# Force openssl-sys to staticly link in the openssl library. Necessary when
+# cross compiling to x86_64-unknown-linux-musl and 32 bit.
+vendored = ["openssl-sys/vendored"]
+