A few fixed misspellings, authorizenet required fields questions, and a trial cron question

My first go at a pull request here. This is adam@adverse.co so you can match up my github with a name (new to github as well).

We're subscribed for support with user "adverse", is this how you would prefer fixes and/or questions to the PMPro plugin or would the private forums be more appropriate? I figured my commits with questions would make it easy for you to analyze if/where any changes would be made (if my questions are valid, that is).

Thanks Jason!