Added integration tests for Apple Mail and Thunderbird

There are five failing tests:

  * should parse Apple Mail (attachment - PGP/MIME): Encrypted and signed ([testmessage](https://github.com/whiteout-io/mail-html5/blob/dev/WO-292/test/integration/email-dao-test.js#L63-L67), [failing line](https://github.com/whiteout-io/mail-html5/blob/dev/WO-292/test/integration/email-dao-test.js#L470))
  * parse Apple Mail (no attachment): Encrypted and signed ([testmessage](https://github.com/whiteout-io/mail-html5/blob/dev/WO-292/test/integration/email-dao-test.js#L67-L71), [failing line](https://github.com/whiteout-io/mail-html5/blob/dev/WO-292/test/integration/email-dao-test.js#L492))
  * should parse Thunderbird (attachment - PGP/MIME): Encrypted and signed ([testmessage](https://github.com/whiteout-io/mail-html5/blob/dev/WO-292/test/integration/email-dao-test.js#L87-L91), [failing line](https://github.com/whiteout-io/mail-html5/blob/dev/WO-292/test/integration/email-dao-test.js#L602))
  * should parse Thunderbird (no attachment): Encrypted and signed ([testmessage](https://github.com/whiteout-io/mail-html5/blob/dev/WO-292/test/integration/email-dao-test.js#L91-L95), [failing line](https://github.com/whiteout-io/mail-html5/blob/dev/WO-292/test/integration/email-dao-test.js#L624))
  * should parse Thunderbird (no attachment): Signed ([testmessage](https://github.com/whiteout-io/mail-html5/blob/dev/WO-292/test/integration/email-dao-test.js#L107-L111), [failing line](https://github.com/whiteout-io/mail-html5/blob/dev/WO-292/test/integration/email-dao-test.js#L712))