Update changelog for v0.4

Changelog.md

@@ -1,4 +1,8 @@
 # Changelog
+# v0.4
+ - Embedded the hash of the commit that cscz was built from into the resulting binary (#3)
+ - Added support for namespaces
+ - Created initial standards document
 
 # v0.3
  - Fixed constructor generation with --public flag (#4)