Fixed #307. Run test_scan requires whitelisting localhost.

This is merely a documentation fix. If anyone intersted in
running the full test suite, or at least test_scan.py, the
runner must ensure localhost is whitelisted. This is achieved
by creating scan.json and whitelist 127.0.0.1.
Merge pull request #308 from yeukhon/issue#307

Fixed #307. Run test_scan requires whitelisting localhost.