add test for get_config FIX
add more testing ability to run_tests

1. python run_tests.py <APP_ENGINE_SDK_PATH> tests
2. python run_tests.py <APP_ENGINE_SDK_PATH> tests/test_models.py
3. python run_tests.py <APP_ENGINE_SDK_PATH> tests.test_models.WikiPageGetConfigTest
Merge pull request #5 from jangxyz/FIX-get_config

Fix Wikpage.get_config