Use TCPSocket.upgradeToSecure() instead of the starttls library.
Force STARTTLS upgrade attempt even if the server doesn't support it.
Unify secureConnection and ignoreTLS options for simplicity
Bug 847032 - don't allow a HELO-based bypass
Merge pull request #2 from asutherland/starttls

Bug 847032 - [email] IMAP only supports initially-SSL encrypted connections, STARTTLS upgrade not supported from unencrypted cleartext. r=asuth