Improved visual experience for MPlayer on macOS

Current versions

mplayershell requires the following formula to be installed:
mplayer 1.3.0 UNIX movie player

Recent formula history

Mike McQuaid mplayershell: remove default_formula requirement.
Izzy Navedo Replace references to “(Mac) OS X” with “macOS”.
Mike McQuaid Use hash rockets again. (#5177)
Mike McQuaid Use Ruby 1.9+ symbol hash keys in all formulae. (#4942)
Mike McQuaid mplayershell: fix strict audit.

Formula code at GitHub