Merge pull request #176 from dh-tech/release/0.8.0

Release v0.8.0

Tagging version 0.7

v0.6.1 - update readthedocs build ubuntu version

v0.6 - experimental omnibus parser / converter

v0.5.2 bugfixes for repr, comparisons, non-Gregorian month durations

v0.5.1 - Make CITATION.cff valid (license id)

v0.5 - UnDelta, UnInt, weekdays, and calendar improvements

v0.4 - Calendar converters, interval improvement, etc.

v0.3.1 - fix readthedocs config

v0.3 numpy datetime64, more EDTF support, better documentation