[RFC] Simplified Homebrew formula

Removed unnecessary cmake modifications, and manual building of
dependencies. Updates to Makefile remove the need.
`make CMAKE_EXTRA_FLAGS="-DCMAKE_PREFIX_PATH=#{prefix}" install` does in fact work, if we want to just do it that way. However, the wiki instructions on installation are to run `make`, and then `make install`. Is it better to follow the wiki, or use the least amount of commands possible?