Parametrize vroom size

[franla23]

This pull requests covers the following minor changes:

• support of VROOM_CONNECTION_SIZE parameter again and removal of hard coded value
• installation of conda-forge::r-iotools=0.3-2 in sequenza environment as the newer version is not compatible with sequnza=3.0.0
• update of readme. It now describes that the reference file must not contain alternative chromosomes and must be sorted.

[priesgo]

The tests are failing, but it is nothing related to these changes so I am approving it.

This brings two things to discuss:

1. the nf-core/modules repo is not linked to any particular commit, branch or tag, so this is out of control from our side. This should be in .gitmodules.
2. I suspect the nf-core module may be genuinely failing now, which would put under question on the usefulness of reusing in this situation. Maybe you could with a quick copy-paste of this gcwiggle module see if you can reproduce the issue locally?

[priesgo]

Good point, it would be good to have this in every tronflow repo, but this is obviously very difficult to maintain. Maybe we could have generic instructions when possible in the documentation and keep README files to a minimum. Just thinking aloud... maybe we can discuss in the larger group next week.

[priesgo]

@johausmann on your question about reusing from nf-core. I suspect one module from nf-core here may be failing. This may be caused by a change in the dependency tree, which can always happen, but it also shows that reusing nf-core may not protect us from this and on the other hand it may slow us down as fixing it in nf-core is less straightforward than fixing it on our side.