Always use an SSL context. [Fixes #548]

This reverts commit 9890b19, as latest
patch releases of 1.8.7 do accept an OpenSSL context object.

This has been broken since the refactoring d6e25e5,
which increased the scope of the original breakage.

Backports c7318a6 to 2-5-stable.

Closes #730

lib/mail/network/delivery_methods/smtp.rb

@@ -129,15 +129,11 @@ def ssl_context
         openssl_verify_mode = "OpenSSL::SSL::VERIFY_#{openssl_verify_mode.upcase}".constantize
       end
 
-      if RUBY_VERSION < '1.9.0'
-        openssl_verify_mode
-      else
-        context = Net::SMTP.default_ssl_context
-        context.verify_mode = openssl_verify_mode
-        context.ca_path = settings[:ca_path] if settings[:ca_path]
-        context.ca_file = settings[:ca_file] if settings[:ca_file]
-        context
-      end
+      context = Net::SMTP.default_ssl_context
+      context.verify_mode = openssl_verify_mode
+      context.ca_path = settings[:ca_path] if settings[:ca_path]
+      context.ca_file = settings[:ca_file] if settings[:ca_file]
+      context
     end
   end
 end