hsevm: project was renamed to hevm

This also upgrades the hsevm package from v0.6.4 to v0.8.5.

The project `dapp` which depends on hsevm was also updated to use the
new name, so I have also upgraded that package from version v0.5.3 to
v0.5.7.

I also added a `dontCheck` to a Hackage dependency because its test
suite depends on Git and runs a bunch of Git repository manipulations.