Defend against unusual Homebrew setups

To aid in Tap transition.  Require Homebrew 0.9.5, rescue
`rename_tags_dir_if_necessary` (`respond_to?` won't work there
because `rename_tags_dir_if_necessary` is a private method.

References: #4192, @Jackiebo in #4096
Merge pull request #4229 from rolandwalker/defend_unusual_homebrew

Defend against unusual Homebrew setups