Remove dependency on data-default-instances-base, and bump base version

[Xitian9]

data-default-instances-base is not on stackage, and this is a blocker for getting this project on stackage (see #12).

However, in 2016 data-default-instances-base was made a no-op which just re-exports instances from data-default-class, which we already depend on. It can therefore be safely removed.

[Xitian9]

An as aside, current sentiment seems to be moving against the usage of Default in code. It might be worth reducing reliance on it in general, replacing/supplementing things like instance Default a where def = … with things like:

defA :: a
defA = …

-- Optional
instance Default a where def = defA

[muesli4]

Nice.

An as aside, current sentiment seems to be moving against the usage of Default in code.

I wasn't happy with it either. The way they enable putting together options in optparse-applicative is really one of my favorites. But let us discuss that in the related thread.