Tagging 0.3.34

Feat croniter_range(start, stop, cron)

Optimization for poorly written cron expression

- Optimized for duplicate entries in a cron expression.  For example if min
  contains '1,5-8,8,5' this can be reduced from [1,5,5,6,7,8,8]
  to simply [1,5,6,7,8].
- Replaced full ranges with a wildcard.  So if mins contain '0-59', this can be
  swapped with "*".  Detecting a "full" entry is possible because of existing
  bounds checking, min value substitution, duplicate removal (new), and max
  value identification (LEN_MEANS_ALL).  So a poorly written hour expression
  like '1-20,0,15-23' can also be reduced to simply "*".

Add new unittest cases with real-world examples of poorly written cron
expressions created by end-users (who aren't cron experts).  Specific
optimizations opportunities include:
- Range reduction:  Minutes of 0-59 can be replaced with "*".
- Removal of duplicate values: Hours of 4,1-4,5,4 can be simplified to 1-5

- Added another unit DST unit test.  Core croniter handles this correctly,
  likely an issue elsewhere in my code.  Adding this for reference.

- Removed the timezone check for the croniter_range() check, it seemed like a
  good idea, but became more trouble that it's worth.  The behavior is well
  defined.  The timezone from 'start' is used and the one from 'stop' is
  only used for terminating the generator, it's up to the user to select
  timezones combinations that make sense.
- Replaced unitest.  New unit test ensures that croniter_range() works across
  DST boundaries.

- Switched to use `issubclass()` for datetime check instead of issubclass, as
  supporting custom classes derived from datetime isn't really supported
  anywhere else so the previous code was awkward and unnecessary.
- Tentatively mark first release as 0.3.34.

- Revamp some internal implementation details of the croniter_range() function.
- Ran flake8 for some cleanup & confirmed with tox
- Fixed coverage of croniter_range(): 100%

- Allow the ret_type to differ from the provided start/stop type.  This is
  closer to the behavior of the croniter() class.  The one difference is that
  if you don't specify 'ret_type' it will autodetect the input type and return
  the same type, which is nice, since that's likely the typical use case.

- Created new helper function `croniter_range()` that allows forward or reverse
  time range iteration based on a given cron expression.  Initial implementation
  handles `ret_type` in a way that's a bit different than the croniter class.
- Added several test cases to a new test class to keep croniter and
  croniter_range cases cleanly separated.
- Updated README to include example use of croniter_range().

Add dateutil unittests & docs

Minor DST unittest tweak

Feat/support for day or

- Block coverage files created by 'coverage run' and 'coverage annotate'
- Skip the '.python-version' file associated with pyenv

- Update some `interpreted text` markup with ``inline literals``
- Note version that 'match' was added - 0.3.32
- Add a missing trailing '::'

- Add a dateutil.tz unittest to ensure that tz implementation gets tested.
- Updated README to note an example with the python_dateutil module.
- Updated the pytz DST example too, giving users a full example to borrow from.

Fixed assertion against wrong variable (typo)

Devs

This fixes #127