Add changelog

CHANGELOG.md

+# Changelog
+
+## 1.0.0-alpha3
+
+* Save runtime dependencies (e.g., jquery, tether) as peer dependencies.
+* Remove unused package dependencies.
+
+## 1.0.0-alpha2
+
+* Remove NCSA license until properly approved.
+
+## 1.0.0-alpha1
+
+* Create proof-of-concept package and documentation.
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