Fix brew audit warnings and cli build failure

[scribblemaniac]

This PR was initially just to fix the warnings produced by brew audit --strict gridcoin. As I went through them, I ended up doing multiple other little things here and there. In the end, this PR does the following:

• Fix all brew audit warnings. These are all just stylistic changes to match core Homebrew formulae.
• Fix cli build failure. The install block for --with-cli does some weird and unnecessary things, and references the makefile.osx which as far as I can tell was removed a long time ago. It works now though.
• Add --without-qrencode flag. This was an option built into gridcoin so we might as well have a flag for it.
• Add implementation for test block. Just gets the version or help menu to see if the executables work.
• Run unit tests when installing. Many core Homebrew formulae seem to do this, and the Gridcoin docs recommend it as well.
• Disable built-in upgrader. Currently this does nothing because the built-in upgrader was removed from the client, but add it anyway for when/if it is added back. This would be desireable since brew upgrade already handles upgrading.

[Git-Jiro]

Hi! Before I merge this, can you remove the License stanza again? It seems to break the macOS 10.3 compatible build in Travis CI.

[scribblemaniac]

Let me look into this. I have 10.13 and the formula installs just fine on it.

[Git-Jiro]

Ok interesting. Then most probably the Homebrew version in the Travis CI image is outdated.

[scribblemaniac]

Yes Travis almost never seems to update their images. I assumed it wouldn't be a problem because Homebrew usually automatically runs brew update before starting many commands, but Travis also explicitly disabled that: https://travis-ci.org/github/Git-Jiro/homebrew-jiro/builds/742337948#L60. I've added a call to brew update and it's working now. This is probably a good idea to do anyway to make sure the dependencies are all up to date. I also had to separate the dependency installation into a different step since that adds just enough time for travis_wait to time out.