New feature and a bug fix

Feature:

• Update base.ts to accept functions for folder name, thanks to Drew Dimanlig wswebcreation/webdriver-image-comparison#23.
  • allow baselineFolder to be a string or function that is passed an options object
  • allow screenshotPath to be a string or function that is passed an options object
    See baselinefolder for more information

Fix:

• The hiding and showing of the scrollbar during a fullpage screenshot on Linux gave inconsistent results, see wswebcreation/webdriver-image-comparison#21 and wswebcreation/webdriver-image-comparison#22. Tnx to Antonello Caboni for the research

Contains:

• Feat: update to latest version of webdriver-image-comparison 815b56f

v1.1.0...v1.2.0