Updated CHANGELOG

CHANGELOG.md

+stable (hotfix) - 2020-04-17
+===================
+
+bug fixes
+---------
+ * Parametric Section: critical depth does not converge on a closed circular section
+ * Uniform Flow: error in speed calculation
+ * Jet Impact: problem with fatal errors strategy
+ * Strickler coefficient's unit
+ * Make solver more robust when searching for start interval
+
 stable (hotfix) - 2020-03-12
 ===================