not using `this` context so much

[ianstormtaylor]

i'm not a fan of relying on this inside iterators because it feels really magicky, and i think its one of the bad parts of jquery.

for some of the cases, it's already duplication, so we could easily just invoke the functions directly and let it be window like normal

for other cases, i'd propose a signature of el, i, list if we decide that el is the default people want. otherwise list, el, i if we think that list is more frequent

what do you guys think? open to suggestions, just feels really bad doing this.hasClass inside filter and such