Bump openssl version

Author: sfackler

Cargo.toml

@@ -31,7 +31,7 @@ phf = "0.7"
 rustc-serialize = "0.3"
 net2 = { version = "0.2", features = ["nightly"] }
 chrono = { version = "0.2.14", optional = true }
-openssl = { version = "0.6.4", optional = true }
+openssl = { version = ">= 0.6.4, < 0.8", optional = true }
 serde = { version = "0.3", optional = true } # Delete for 0.11
 serde_json = { version = "0.6", optional = true }
 time = { version = "0.1.14", optional = true }