Remove support for 0.5 and drop Compat

[iamed2]

Compat wasn't used anymore so I dropped it. If we need it again we can find a new lower version bound.

I also bumped up the IntervalSets dependency.

[iamed2]

@mbauman @ajkeller34 thoughts on this?

I also have a branch where I've made some improvements using 0.6-only syntax and would love to push that as well, and get #88 in.

[ajkeller34]

Looks good to me, though over in #97 @timholy seemed to lean towards finishing and merging #90 before dropping 0.5 support. I'm not sure what the status of that is.

[iamed2]

I don't think anyone's around to work on that so I think at this point we could backport it to a 0.5 branch+tag if it gets in to a newer version.

[ajkeller34]

Ok, I tend to agree. I'll merge this in a few hours if I don't hear from anyone else. I'll close/reopen this PR to trigger CI again in the mean time.

[iamed2]

Thanks!