Avoid having "@" as the first char in curl_setopt with CURLOPT_POSTFIELDS

Strings starting with a "@" are treated as file uploads by curl in PHP.

See: http://www.php.net/manual/en/function.curl-setopt.php (-> CURLOPT_POSTFIELDS)

So, if a message starts with a `"@"` the quick-fix is to add a space to the front of the message. Although this feels like a hack, there seems to be no other way.