DOC: add human-readable CHANGELOG

Author: pavoljuhas

CHANGELOG.md

@@ -0,0 +1,33 @@
+# Release notes
+
+## unreleased - Version 3.0.0
+
+Differences from version 1.3.
+
+### Added
+
+- Support for Python 3.7, 3.6, 3.5 in addition to 2.7.
+
+### Changed
+
+- Always use lower-case imports from `diffpy.structure`.
+- Use numeric-value sort to order variables in `PrintFitHook`.
+
+### Deprecated
+
+- Variable `__gitsha__` in the `version` module renamed to `__git_commit__`.
+
+### Removed
+
+- Optional upper and lower-bound arguments in `Parameter.setValue`.
+  The bounds can be set with `Parameter.boundRange` instead.
+- Unused classes `ListOperator`, `SetOperator`.
+
+### Fixed
+
+- Metadata retrieval from `PDFContribution` hierarchy.
+- Refresh `PDFGenerator` when its `rgrid` is changed in-place.
+- Zero division in the `nppdfsas.py` example.
+- Crash in `ellipsoidsas.py` example because of bug in `Parameter.setValue`.
+- Pickling of `ProfileGenerator` objects and of bound class methods.
+- Invalid escape sequences in string values.