Add changelog

Includes the changelog to keep track of the different versions and
release dates.

CHANGES.md

@@ -0,0 +1,37 @@
+Changelog
+=========
+
+v0.1.1 (2022-01-29)
+-------------------
+
+### New
+
+- Includes a convenience function for atmospheric scale height
+
+### Changes
+
+- CI and CD switched from travis to Github actions
+- Documentation updates
+
+
+v0.1.0 (2021-06-25)
+-------------------
+
+### New
+
+- Beta release.
+
+
+v0.0.2 (2020-08-14)
+-------------------
+
+### New
+
+- Provides "wheels" for linux, OSX, and Windows
+- Includes experimental `xarray` dataset interface
+
+
+v0.0.1 (2020-02-07)
+-------------------
+
+Initial alpha release.