Improve pre-commit sample for openwhisk (#72)

The current code sample does not scan the full openwhisk directory but only starting from the current directory. In addition, no configuration file is specified.

With this change, the pre-commit hook scans the full openwhisk directory and uses the scan configuration that is also used in the openwhisk Travis configuration.
diff --git a/README.md b/README.md
index ad37e5a..8966979 100644
--- a/README.md
+++ b/README.md
@@ -64,9 +64,12 @@
 $ cat /path/to/openwhisk/.git/hooks/pre-commit
 #!/usr/bin/env bash
 
+# -- Code scanning --
+# See https://github.com/apache/openwhisk-utilities
 # determine openwhisk base directory
 root="$(git rev-parse --show-toplevel)"
-python /path/to/openwhisk-utilities/scancode/scanCode.py . --config $root/tools/ --gitignore $root/.gitignore
+scancode_path="/path/to/openwhisk-utilities/scancode"
+python $scancode_path/scanCode.py --config $scancode_path/ASF-Release.cfg --gitignore $root/.gitignore $root
 ```
 
 _Note_: A hook a locally installed, so if you check out the repository again, you will need to reinstall it.