Update zdde.py

resolving spelling mistake
slide changes to be able to use non-zemax-functions on unix

Author:    xy124 <qcd@gmx.net>
Merge branch 'master' of github.com:xy124/PyZDDE
more fixes for os independence
merge in v0.8.0
Merge branch 'master' of https://github.com/indranilsinharoy/PyZDDE
added zUnitToMeter to easily handle zbf-units
slide formatting change
Merge branch 'master' of https://github.com/indranilsinharoy/PyZDDE

Conflicts:
	pyzdde/zdde.py
removed _debugprint calls, adapted errorhandling for python3
Merge branch 'master' of https://github.com/indranilsinharoy/PyZDDE

Conflicts:
	pyzdde/zdde.py
fixed import *
slide formatting issues
Merge pull request #36 from xy124/master

Some python3 adaptions, introduced zUnitToMeter, OS independence