Update to construct 2.9

[gileri]

I'm trying to package a project that use pymp4, but find it challenging as pymp4 is based on construct 2.8, while construct 2.9 is now the default version in repositories..

There are a number of breaking changes, and I'm aware that the project hasn't received commits in a year, but it would be nice to be able to package pymp4 against recent version of its dependencies.