Allow newer versions of pylint

The .pylintrc used for neutron refers to checks added in pylint 1.3.0,
and aborts on earlier versions (from a quick experiment).

This change moves from a strict pylint==0.25.2 pin to allow newer
versions, as a first step to moving to pylint>=1.3.0.

Change-Id: Ia293eb1329f2c1c2894ab7d8d2142951e670fbaf
Merge "Allow newer versions of pylint"