Fix Waterline typo

[mikehdt]

Fixes a small typo in the docs where "Waterline" was misspelled.

[sailsbot]

Hi @mikehdt! It looks like the title of your pull request doesn’t quite match our guidelines yet. Would you please edit your pull request's title so that it begins with [proposal], [patch], [fixes #<issue number>], [implements #<other PR number>], or [misc]? Once you've edited it, I'll take another look!