Fix installation into user directory

[fdcds]

This allows pip install --user SafeEyes or python setup.py install --user to work.

[slgobinath]

@fdcds thank you for your contribution.

[TPXP]

This causes an issue when packaging SafeEyes: it will install stuff to the home directory of the user who built the package.
I implemented a workaround on the AUR package for safeeyes-git, but it's probably not the best idea. Perhaps try catching the --rootdir argument, or add a --system option?

See my comment on the AUR (and the reports below): https//aur.archlinux.org/packages/safeeyes-git/#comment-762203
My workaround: https://aur.archlinux.org/cgit/aur.git/commit/PKGBUILD?h=safeeyes-git&id=5477aa5e6c17393f56506ae39bd4dcd925288745

[slgobinath]

@TPXP I'm terribly sorry for not replying you. I missed your comment and just noticed it while checking your AUR package. First of all thank you very much for maintaining the safeeyes-git AUR.

For this particular issue, if you have any solution, I'd appreciate a PR. I'm bit busy with some personal commitments. I will get back to this when I get some time.