Ability to get captchas when submitting content.

First ever submission with jarecli was done in /r/prawtesting a few minutes ago.

Before, submitting was impossible if a captcha was required. This implementation still has two limitations:
* it uses ncurses addstr, which will traceback if two many lines of text are submitted
* it is unknown what would happen if a captcha is given incorrectly. Probably a fatal InvalidCaptcha exception.

TODO:
* fix bugs above
* give a message about msg submitted
* reload current subreddit so the new submission can be found