Feat/parse only single file

[saimonnozaki]

Overview

This is a feature request.

Our project appreciates this awesome project, because its has so many class style components.
By the way, we want to migrate .vue file one by one checking passing unit tests.

So, this feature request proposes that vue-class-migrator can parse CLI option -f same as -d.

Design

vue-class-migrator...

• can parse an option of single file migration
  • Add migrate function of entry point
• can parse -d option same as before
  • partially generalized migration promise
• force select either -f or -d
  • Add OptionParser class to force option selection

Checks

I checked that...

• -f option works
• adding unit tests and existing tests does not break

[saimonnozaki]

OptionParser guarantees option requirements

[saimonnozaki]

@victorcuena

Hello, thank you for such an awesome project.

Would you please review this feature request?

[victorcuena]

Thanks a lot for the PR, I just added a comment, the rest looks good to me.

[saimonnozaki]

@victorcuena

Thank you checking my PR. Sorry but, I cannot see where your comment is. Did you leave comment on the code diff?

[saimonnozaki]

@victorcuena

Thanks alot for your review! I fixed it, would you please review this again?