Don't warn "Found multiple files" when they are the same file

[TSMMark]

Solves this comment #62 (comment)

I tested locally by installing from dev build like:

yarn vscode:prepublish
yarn global add vsce
$(yarn global bin)/vsce package
code --install-extension ruby-rubocop-0.8.6.vsix

And I no longer get the warning:

[Skipants]

@TSMMark This change is awesome, much needed, and can't wait to see it merged. I hope you don't mind my random review -- I noticed this can be simplified slightly.

[TSMMark]

Can this get a review + merge + release from a maintainer? Thanks