raise on fillna passed a list or tuple
fixes #3435.

pls add a release notes mention (and in general if its worth of the whatsnew a mention of that too)
 @jreback Okay. Rule of thumb for when to add a rls notes mention?
 pretty much anything non-trivial should get in release notes (or trivial but its a API change or bug)

if its a separate issue (e.g. documented), I always put in release notes with an issue link. Docs don't bother (unless again it has an actual issue attached, e.g. #3566) whatsnew if it is an non-trivial API change, or you want to 'announce' it, e.g. your regex stuff will certainly need a whatsnew (and docs), as its useful and new behavior. I just do a quick ipython (usually based off the tests), or you have doc strings, whatever works.

so this needs a mention (as its an issue). If you had just discovered this (and not an op), then maybe doesn't make much difference as a future user would then read the doc string and not be suprised (or get the exception).
 cool. great explntn.
 this looks ready for merge, yes?
 @cpcloud can you rebase....this is the annoyance with release notes. the fact that I merged something in a different order causes these things to not be auto mergable.....thxs
 @jreback rebased
 better commit message
