Revert "travis: bump to Qt 5.9.1"
Revert "travis: bump to Qt 5.9.1"

This reverts commit e82b0d4088b6a6ce81d6495c6e66da60113c1177.

plugz/qlcplus,mcallegari/qlcplus,mcallegari/qlcplus,mcallegari/qlcplus,plugz/qlcplus,plugz/qlcplus,mcallegari/qlcplus,kripton/qlcplus,sbenejam/qlcplus,sbenejam/qlcplus,sbenejam/qlcplus,kripton/qlcplus,sbenejam/qlcplus,plugz/qlcplus,sbenejam/qlcplus,sbenejam/qlcplus,kripton/qlcplus,plugz/qlcplus,kripton/qlcplus,plugz/qlcplus,mcallegari/qlcplus,sbenejam/qlcplus,mcallegari/qlcplus,kripton/qlcplus,plugz/qlcplus,mcallegari/qlcplus,kripton/qlcplus,kripton/qlcplus