Update CHANGELOG and require updates in future PRs

.github/PULL_REQUEST_TEMPLATE.md

@@ -8,3 +8,4 @@ I'll review the commits, so I mostly want to understand the "why" rather than th
 - [ ] Same for documentation, including moduledocs
 - [ ] Tests were added or updated to cover changes
 - [ ] Commits were squashed into a single coherent commit
+- [ ] Notes added to CHANGELOG file which describe changes at a high-level

CHANGELOG.md

@@ -5,10 +5,32 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 ## Unreleased
 
-## 3.5.1
+- TBD
+
+## 3.6.1
+
+### Potentially Breaking
+
+- Require Elixir v1.6+
+
+### Added
+
+- Setup property based test framework and add sample tests (#480)
+- Turkish translation (#534)
+- Add details to parsing documentation (#540)
+- Support time units in singular (#509)
+- #538 documentation of default formatting directives
+- Support for tzdata 1.0.0 (#536)
 
 ### Fixed
 
+- Address handling of ambiguity in timezone conversions by using UTC clock time, where possible. See #488
+- #491 gracefully handle errors resolving a timezone using wall clock time
+- #514 gracefully handle converting date to datetime on tz boundary
+- #531 address some issues with shifting over timezone boundaries
+- #507 unnecessary tz conversion during logical shifts results in erroneous results
+- #532 shift priority incorrectly inverted
+- #537 precision not preserved in some situations
 - Elixir 1.8 deprecations
 - `Timex.diff/2` spec
 - `Timex.Timezone.convert/2` when using custom time zones