Resolve "Best way to get number of hit DOMs"

Closes #46

See merge request !31

More information can be found at https://github.com/scikit-hep/awkward-1.0/issues/219

Resolve "Closing the files?"

Closes #47

See merge request !30

Resolve "Error when trying to get track info"

Closes #45

See merge request !29

There are obviously no wheel packages for newer versions
available (yet), so the installation fails with
`llvm-config` not found since it tries to compile it.