adding note about model error to read me

README.md

@@ -7,6 +7,12 @@
 
 <!-- badges: end -->
 
+# Critical News:
+## Error in the non-hierarchical first-difference model
+In versions 1.1.0, 1.1.1, and 1.1.2.0, the non-hierarchical variant of the first-difference model included a coding error. Estimates of trends and population trajectories from this model in these versions will be biased. 
+The error was fixed in version 1.1.2.1.
+I so sorry for this error, please [reach out](https://github.com/AdamCSmithCWS) if you would like more information or assistance in fixing/recovering from this. 
+
 # bbsBayes2 <img src="man/figures/logo.png" align="right"/>
 
 bbsBayes2 is a package for performing hierarchical Bayesian analysis of North