Added support for local setup/teardown functions

test/test_helper.bash

@@ -13,11 +13,23 @@ if [ "$BASH_IT_ROOT" != "${BASH_IT_TEST_DIR}/root" ]; then
   export BASH_IT=$BASH_IT_TEST_DIR
 fi
 
+local_setup() {
+  true
+}
+
+local_teardown() {
+  true
+}
+
 setup() {
   mkdir -p -- "${BASH_IT_ROOT}"
+
+  local_setup
 }
 
 teardown() {
+  local_teardown
+
   rm -rf "${BASH_IT_TEST_DIR}"
 }