Improved docs on Transforms

[tempdata73]

Notes:

• I didn't use vl's example of using argmax on the movies dataset because this whole page uses the cars dataset as a guide. I felt like using the former would break the flow of thought. Nonetheless, I can happily incorporate it if you guys prefer that one.

Sorry for messing up the other pull request (#2654), but I finally fixed my commits and branches.

[mattijn]

Thanks for the PR! No problem of messing up the commits. Me or @joelostblom will do a review somewhere in coming days.