Fix flake errors
Make parse_datetime raise ISO8601Error if no 'T'

- Make parse_datetime raise ISO8601Error if time designator 'T' is missing
  as before it would raise a ValueError that was hard to interpret.
- Alter test_parse for test_datetime to check that bad inputs raise an
  ISO8601 error. The other tests did this, but test_datetime didn't.
- Add test case where the 'T' time designator is missing from input
  datetime strings.
fix duration pickle for all protocols and all supported python versions and variants. (closes #10)
Merge pull request #11 from tofu-rocketry/flake_fixes

Fix flake errors
Merge pull request #12 from tofu-rocketry/datetime_input_handling

Make parse_datetime raise ISO8601Error if no 'T'
add Python 3.4 to list of supported versions
release 0.5.1
bump to 0.5.2-dev