blockhash 0.2

[ilovezfs]

• Have you followed the guidelines for contributing?
• Have you checked that there aren't other open pull requests for the same formula update/change?
• Have you built your formula locally with brew install --build-from-source <formula>, where <formula> is the name of the formula you're submitting?
• Does your build pass brew audit --strict <formula> (after doing brew install <formula>)?

---

remove ImageMagick 7 fix since it's no longer needed
update hash in the test since the algorithm has changed
switch to shell_output in the test since the exit code should now be 0