Update nrrd.py

Fixes problem opening in ImageJ/Fiji with 'space dimension' not being provided before 'space' and defaulting to 0 resulting in miss-match.
Update nrrd.py

Duplicate open request?
Merge pull request #5 from Robbie1977/patch-1

Update nrrd.py
Merge pull request #6 from Robbie1977/patch-2

Update nrrd.py
Fixed writing relative file name when using a separate header.
Merge pull request #7 from jaspervdg/master

Fixed writing relative file name when using a separate header.
fixed keyvaluepairs in writing files

Exception was thrown before, because for loop over dictionary only
returns key during the loop. Values would have to be extracted manually
from dictionary using get()
Use of .items() makes old construct possible
Merge pull request #8 from yanlend/master

fixed keyvaluepairs in writing files
Fix indentation (tabs vs spaces).
Merge pull request #1 from mhe/master

Bringing up to date