DOC: add human-readable CHANGELOG

Author: pavoljuhas

CHANGELOG.md

@@ -0,0 +1,35 @@
+# Release notes
+
+## Unreleased - Version 2.1.0
+
+Notable differences from version 2.0.1.
+
+### Added
+
+- Support for Python 3.7.
+- Validation of compiler options from `python-config`.
+- Make scons scripts compatible with Python 3 and Python 2.
+- Support np.array arguments for `SetPowderPatternX`, `SetPowderPatternObs`.
+- Declare compatible version requirements for client Anaconda packages.
+- Facility for silencing spurious console output from libobjcryst.
+
+### Changed
+
+- Build Anaconda package with Anaconda C++ compiler.
+- Update to libobjcryst 2017.2.x.
+
+### Deprecated
+
+- Variable `__gitsha__` in the `version` module which was renamed
+  to `__git_commit__`.
+
+### Removed
+
+- Support for Python 3.4.
+
+### Fixed
+
+- Ambiguous use of boost::python classes and functions.
+- Name suffix resolution of `boost_python` shared library.
+- `SetPowderPatternX` crash for zero-length argument.
+- Incorrectly doubled return value from `GetInversionCenter`.