command line interface

[xjamundx]

• 5to6 filename.js post output to terminal
• 5to6 dirname warns it will need an out directory (or should it work inplace?)
• 5to6 dirname outdir will happily process directory
• 5to6 dirname outdir --ext es6 - moves then and renames files to .es6

Other commands:

• -v or --version
• -h or --help
• 5to6 should just display --help

What other options would we need (besides enabling specific "transforms"?)