Bump the version number to 0.7.5.
Bump the version number to 0.7.5.

Changes since 0.7.4:
- Update the dictionary and UIDs to DICOM 2016a.
- Apply CP-1066 by writing overlength values as UN.

dgobbi/vtk-dicom,dgobbi/vtk-dicom,dgobbi/vtk-dicom