Don't generate subfolders.

Fix #130, see this issue for more informations.
Merge pull request #136 from dduponchel/issue_130

Don't generate subfolders.
Add comment support

This commit add the ability to read and generate comments on the zip
file and/or on each zip entry.
Fix #134.
update build dependencies

The old version of the saucelabs plugin may explain why I couldn't run the
saucelabs tests.
I'm also upgrading the other build dependencies.
move ZipObject and JSZip attributes

Now `date`, `dir` and `comment` are attributes of `ZipObject`.
See #137 for more details.