Bug#742557: pytables: debug package should depend on numpy-dbg

[Julian Taylor]

Package: pytables
Version: 3.1.0-2
Severity: normal

python-tables-dbg can't be imported without python-numpy-dbg and
python-numexpr-dbg so it should depend on it instead of only
recommending it.

This also causes the auto package tests to fail:
http://ci.debian.net/#package/pytables
https://jenkins.qa.ubuntu.com/view/Trusty/view/AutoPkgTest/job