Add (production) dependencies in package.json
Replace execSync/sips by image-size

More simple and no dependency with batch script
Fix idBasedOnFilenameCamelized for Windows (backslash case)
Merge branch 'bug-execsync'

* bug-execsync:
  Fix idBasedOnFilenameCamelized for Windows (backslash case)
  Replace execSync/sips by image-size
  Add (production) dependencies in package.json