chore: upgrade solidity-coverage to v0.6+

[sohkai]

cc @facuspagnuolo Let's see how long coverage takes now :).

[coveralls]

Coverage decreased (-0.5%) to 98.0% when pulling 9600e96 on upgrade-solidity-coverage into 7988a73 on master.

[coveralls]

Coverage decreased (-0.2%) to 98.289% when pulling 52cb0d9 on upgrade-solidity-coverage into de4491f on master.

[facuspagnuolo]

since the new solidity-coverage version is using ganache, do we still need this one?

[sohkai]

I think so, the reason was that lerna hoisting makes running testrpc-sc a bit of a pain unless we explicitly declare this dependency here.

[facuspagnuolo]

I see, but I we shouldn't need to run it anymore right?

[sohkai]

I think we still have to; the ganache-cli.sh script runs testrpc-sc and AFAIK coverage still requires the modified version of testrpc.

[sohkai]

So... looking into this a bit more, unfortunately there's no good way to get Payroll to compile on a coverage environment.

solidity-coverage preprocesses all copied npm dependencies, and in our case, this leads to some mismatches between skipped test files and their dependencies (specifically, the ERC20 from @aragon/os and MaliciousToken).

solidity-coverage has said recently that they'll be moving away from requiring any preprocessing step, and we can revisit this once that's ready. It's also highly unlikely at the current moment that Payroll's coverage tests would run without requiring us to split them up, like we did for normal tests :).