Bump numpy from 1.15.3 to 1.15.4
Bump numpy from 1.15.3 to 1.15.4

Bumps [numpy](http://www.numpy.org) from 1.15.3 to 1.15.4.

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
vberlier/nbtlib