README: how to install mplayer with homebrew

Applies to OS X instructions.
Merge pull request #131 from vitorgalvao/patch-1

README: how to install mplayer with homebrew
Allow setting ddir using ~/path/
Merge pull request #136 from punchagan/set-ddir-expanduser

Allow setting ddir using ~/path/
Fix setting expanded ddir (#136)
Updated changes
Added troubleshooting link
Merge branch 'develop' into autodetect-terminal-size