Issue 668: Fix logging out on windows

[B-E-A-F]

Fixes #668

I removed the del library, as it was only used in this one location. For more info read Issue.

There was a comment about relative paths not working for the del library? That may or may not be relevant now, but I looked over the functionality and I believe that you still need both lines.

• npm run test succeeds.
• npm run lint succeeds.
• Appropriate changes to README are included in PR.

[B-E-A-F]

Forgot to run the linter 😭. I see some code that was actually merged with some linting issues as well.

[grant]

Thanks!

Here's the error from Travis:

ERROR: /home/travis/build/google/clasp/src/commands/openCmd.ts:73:71 - Type declaration of 'any' loses type-safety. Consider replacing it with a more precise type.
ERROR: /home/travis/build/google/clasp/src/commands/openCmd.ts:76:39 - Missing trailing comma

[grant]

Awesome