DEP: bump numpy min version?
We currently require 1.13.3 which was released 2017-09-29.  The last bump was in 0.25.0 (#25554).

I think its time for another bump.  The release dates for the 1.x.0 and 1.x.MAX versions out there:

1.14.0 -> 2018-01-06
1.14.6 -> 2018-09-23
1.15.0 -> 2018-07-23
1.15.4 -> 2018-11-04
1.16.0 -> 2019-01-13
1.16.6 -> 2019-12-29
1.17.0 -> 2019-07-06
1.17.5 -> 2020-01-01

1.15.4 looks not-unreasonable to me.