Stop using NUMPY_MMAP constant

[effigies]

Summary

This is now always True:

nipype/nipype/utils/config.py

Line 31 in 388f140

NUMPY_MMAP = LooseVersion(np.__version__) >= LooseVersion("1.12.0")

nipype/nipype/info.py

Line 104 in 388f140

NUMPY_MIN_VERSION = "1.12"

All of its uses can now be removed.

[iugastefan922]

Hi, I would like to contribute on this one.

[effigies]

Great! Please let us know if you need any help getting started.

[effigies]

Closed in #3121.