handle --help for subcommands
handle --help for subcommands

If subcommand is provided (and exists) and its first arg is -h/--help,
go ahead and intercept the call; redirecting to rbenv-help <subcommand>

This means subcommands and plugins need not handle --help flag
themselves

jeremy/rbenv,jasonkarns/rbenv,bradynpoulsen/rbenv,zmwangx/pyenv,cehoffman/rbenv,cehoffman/pyenv,cehoffman/rbenv,syndbg/goenv,cehoffman/nodenv,sstephenson/rbenv,docwhat/rbenv,syndbg/goenv,nodenv/nodenv,zmwangx/pyenv,rbenv/rbenv,sstephenson/rbenv,cehoffman/rbenv,jrolfs/nodenv,genome-vendor/pyenv,jeremy/rbenv,viclim/rbenv,jrolfs/nodenv,rbenv/rbenv,OiNutter/nodenv,viclim/rbenv,Angeldude/rbenv,jeremy/rbenv,jasonkarns/rbenv,Angeldude/rbenv,nodenv/nodenv,cehoffman/pyenv,pyenv/pyenv,BanzaiMan/pyenv,genome-vendor/pyenv,bradynpoulsen/rbenv,pyenv/pyenv,yyuu/pyenv,BanzaiMan/pyenv,sebhahn/pyenv,yyyc514/rbenv,sebhahn/pyenv,Angeldude/rbenv,yyyc514/rbenv,sstephenson/rbenv,OiNutter/nodenv,bradynpoulsen/rbenv,docwhat/rbenv,sebhahn/pyenv,pyenv/pyenv,syndbg/goenv,cehoffman/nodenv,viclim/rbenv,docwhat/rbenv,yyuu/pyenv,jasonkarns/rbenv,yyyc514/rbenv,syndbg/goenv