feat(ssl): enable hostname verification by default for OpenSSL

Additionally disables SSLv2 and SSLv3, as those are universally considered
unsafe.

Closes #472

Cargo.toml

@@ -32,6 +32,10 @@ default-features = false
 version = "0.7"
 optional = true
 
+[dependencies.openssl-verify]
+version = "0.1"
+optional = true
+
 [dependencies.security-framework]
 version = "0.1.4"
 optional = true
@@ -49,6 +53,6 @@ env_logger = "0.3"
 
 [features]
 default = ["ssl"]
-ssl = ["openssl", "cookie/secure"]
+ssl = ["openssl", "openssl-verify", "cookie/secure"]
 serde-serialization = ["serde", "mime/serde"]
 nightly = []