python-dataproperty: bump to version 0.3.1

python-dataproperty: bump to version 0.3.1

Version 0.3.1 makes pytest-runner dependency optional.

Fixes:
http://autobuild.buildroot.net/results/0c8/0c8e0ceccc2d5f48138ec4f95e57729e33108f59
http://autobuild.buildroot.net/results/eab/eab2d2bf78ac943156a0b8698e63bdf6e63865bf
http://autobuild.buildroot.net/results/4d6/4d60c711e9c1da6dd5bb809bbe328e6252d2d747
http://autobuild.buildroot.net/results/ed1/ed1982367fa1531d772d29b35e333b34e5889cec
http://autobuild.buildroot.net/results/a0e/a0ebb6b155fa11c5886080f993c9aa9d596ac1c3
http://autobuild.buildroot.net/results/85e/85e5086401a314a2d3d24efa887ac0188add85fc
http://autobuild.buildroot.net/results/99e/99ea243303ae12aceb2fac3a5df5e3b552712eda

Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>