fixed issued with the wrong weights being assigned to events.

[Walter-Ullon]

Hello Kim,

I have started going over the code and the simulated data and trying to replicate it all in python-pandas in a local repo to ensure I understand all the steps and can derive things on my own.

I have come across this issue where in the textbook, as well as line 58 of implicit_rating_calculator.py, you designate "moredetails" as w2 (50), but in line 93 you have it switched with "details".

There's one other issue I will create a PR for once I find it, but in listing 4.1 of the textbook, you do a count(CASE... using moredetails as the event, when in fact in should be moreDetails. This is causing the simulated data to contain all zeroes under moreDetails when counting events for users. I have checked this locally and can confirm. This will skew all implicit ratings.

Cheers!