metomi/isodatetime#13: timepoint-like duration e.g. PYYYYMMDD
test timepoint membership in timerecurrence
Add CHANGES.md file
Merge pull request #23 from benfitzpatrick/test_in_timerecurrence

Test for membership in TimeRecurrence
isodatetime: fix recurring recurrence format 1
Merge pull request #25 from benfitzpatrick/fix-iso-recurrence-format-1

isodatetime: fix recurring recurrence format 1
Merge pull request #24 from benfitzpatrick/changes

Add CHANGES.md file
Merge pull request #22 from benfitzpatrick/13.timepoint-like-duration

#13: support timepoint-like duration e.g. PYYYYMMDD
Update CHANGES.md