Parallel serial threshold incorrect

[ihincks]

I would just submit a PR, but am a bit confused about which branch to do it on at this point. Anyway, around line 180 of parallel.py, it should be index 0 I think:

if modelparams.shape[*0*] <= self._serial_threshold:

(also fix theshold typo while at it)

[ihincks]

Note to self: don't forget to mention dview.use_dill() to deal with models that might have closures.

[cgranade]

This should be resolved by #82?

[ihincks]

Yep, thanks.