BugFix Datamark/core.py:
* reading 0.5 datawide (4 bits) data format
* Reads the full channel number as 4 char hex: 0000 to ffff
corrected test issue (now that we read channel id correctly...)
PEP8 cleaning (I don't find it cleaner, but OK)
changelog for obspy.datamark
Merge pull request #721 from ThomasLecocq/fix_datamark

BugFix obspy.datamark
Merge remote-tracking branch 'upstream/releases'

Conflicts:
	obspy/datamark/core.py