update CHANGELOG for arfc#22

CHANGELOG.rst

@@ -13,15 +13,23 @@ Since last release:
 * Add input parameters to `DepleteReactor` for the thermal 
   power (instead of just using `power_cap`) and flux 
   (required input for running OpenMC with new version) (#18)
+* Add CI test for if CHANGELOG has been updated (#21)
 
 **Changed:**
 
 * Change OpenMC dependency to v0.14.0, which includes adding 
   parameters for using `DepleteReactor` (#18)
+* Simplifiy CI build environment, using conda builds instead of 
+  building from source (#21)
+* Depletion time steps are based on `dt` parameter of Cyclus 
+  input (which is in seconds) instead of assuming 30 day time steps (#22)
+
 
 **Removed:**
 
 * Remove `check_existing_recipes` method in `DepleteReactor` (#18)
+* Remove various files in repo that are no longer used for building 
+  CI enviroment (#21)
 
 **Fixed:**