minor wording/punctuation edits to eventmanager tutorial

Hi JumpstartLab team,

I've been finding many of your tutorials and exercises to be very helpful as I'm studying Ruby and Rails. I just reviewed a portion of the eventmanager tutorial to see if I could suggest any improvements to the wording of the instructions (typos, punctuation, voice).

As this is my very first pull request, please let me know if there is anything I could do differently to better contribute.

Best Regards,
Rylee Keys