Avoid StopIteration leak on explicit #next call in #next_occurrence

[#203]
[#213]
Version 0.11.3
Occurrence#overnight? now works for a start_time on the last day of a month
Merge pull request #218 from neckhair/master

Fix: Occurrence#overnight? on the last day of a month
added failing specs for wrong timezone in Schedule#occurrences_between
Ensure all array elements are tested
Ensure all time comparisons are done in schedule zone
Add deprecations and settings for compatibility

Changing :start_date to :start_time everywhere will take a while for
some users due to serialized schedules that still have this key.

For now we'll export both start_time and start_date in serialized
output but this duplication should be removed in the next version.

We will continue to read both :start_date and :start_time, with a
preference for the new :start_time.
Merge pull request #219 from avit/deprecations

Add deprecations and settings for compatibility
Avoid symbolizing input in FlexibleHash
Extract HashParser class

* Add deprecations for old options
* Yield new schedule for setting overrides
* Allow numeric strings for days/months from JSON [#215]
Extract YamlParser class
Allow for stringy hashes when deserializing
Fix wrong variable
Fix YAML hash parsing and 1.9 compatibility
Skip double occurrences over DST

Fixed #189
Use ruby built-in StopIteration
Update changelog for previous releases
Release 0.12.0
Fix markdown