Bug: CSV header written to file is missing `Updates, `

[mrienstra]

While throwing #7 together, I noticed a bug introduced in #5 -- the CSV headers were only changed from
DateTime, Installs, Downloads, Version to
DateTime, Installs, Updates, Downloads, Version in the console.log on line 32, they should've also been changed on line 65 where they are written to the .csv file (as well as in a few comments).

#7 fixes this bug, as a side-effect of generating the CSV headers dynamically from availableStats & requestedStats , and of course, this bug could instead be fixed very easily just by changing line 65!