Add tests.edn to avoid Kaocha warnings

TODO.md

@@ -1,6 +1,5 @@
 # To-do
 
-* Anatomise some payroll data for use as a test case
 * Validation/error handling on CLI arguments - required options like csv, date, period
 * Potentially move employee-name->entity-tag into config
 * Potentially move cat->payroll-type into config

tests.edn

@@ -0,0 +1,4 @@
+#kaocha/v1
+{:tests [{:id :unit
+          :test-paths  ["test" "src"]
+          :ns-patterns [".*"]}]}