[IMP] travis_install_nightly: support wkhtmltopdf 0.12.5
[IMP] travis_install_nightly: support wkhtmltopdf 0.12.5

Currently, only those versions of wkhtmltopdf that come on a .tar.xz are
installable, but not those who come on .deb packages. That includes the
most recent version 0.12.5.

This commit adds support for those versions, which includes 0.12.1 and
0.12.5

Closes #572

OCA/maintainer-quality-tools,acsone/maintainer-quality-tools,OCA/maintainer-quality-tools,acsone/maintainer-quality-tools,acsone/maintainer-quality-tools,OCA/maintainer-quality-tools