The markDirectories option adds extra slashes

[mrmlnc]

Environment

• OS Version: Windows 10 (1903)
• Node.js Version: 12.4.0

Actual behavior

       [
         "fixtures/file.md"
         "fixtures/first/"
      -  "fixtures/first//file.md"
      -  "fixtures/first//nested/"
      -  "fixtures/first//nested//directory/"
      -  "fixtures/first//nested//directory//file.md"
      -  "fixtures/first//nested//file.md"
      +  "fixtures/first/file.md"
      +  "fixtures/first/nested/"
      +  "fixtures/first/nested/directory/"
      +  "fixtures/first/nested/directory/file.md"
      +  "fixtures/first/nested/file.md"
         "fixtures/second/"
      -  "fixtures/second//file.md"
      -  "fixtures/second//nested/"
      -  "fixtures/second//nested//directory/"
      -  "fixtures/second//nested//directory//file.md"
      -  "fixtures/second//nested//file.md"
      +  "fixtures/second/file.md"
      +  "fixtures/second/nested/"
      +  "fixtures/second/nested/directory/"
      +  "fixtures/second/nested/directory/file.md"
      +  "fixtures/second/nested/file.md"
       ]

Expected behavior

Only one trailing slash per entry.

Steps to reproduce

See smoke tests: #215