Widen/Opening-up dependency versions

Currently the dependencies have very narrow versions specified, making it very hard to install Mighty alongside other packages. As we discussed last year, opening up the ceilings of dependency versions would be great.

Start by locating the dependency declaration file and reviewing the currently pinned or capped versions. Identify which ceilings can be widened without changing the requested dependency set, then verify that Mighty still installs alongside other packages and that the existing test suite passes.

Written by the indexing model from the issue text.