fix between_time filtering values

[maurerle]

Set masked values on parts with indexer_between_time to keep the values not in the time with false.
This is actually unrelated to the mask having an error but comes from between_time returning only a subset of the data, which makes pandas loose the other parts of the index.

fixes #64
supersedes #65

I am not particular happy with this solution, but it includes not having errors and not producing warnings

[pep8speaks]

Hello @maurerle! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file src/demandlib/particular_profiles.py:

Line 74:80: E501 line too long (87 > 79 characters)
Line 75:80: E501 line too long (92 > 79 characters)
Line 76:80: E501 line too long (96 > 79 characters)
Line 77:80: E501 line too long (98 > 79 characters)
Line 78:80: E501 line too long (102 > 79 characters)