reverting chai to 4.5 to use with ts-node for a correct coverage report

Author: AleksandrRogov

.mocharc.js

@@ -0,0 +1,6 @@
+{
+    "diff": true,
+    "extensions": ["ts"],
+    "spec": ["tests/*.spec.ts"],
+    "require": ["ts-node/register"]
+}