Added include of utils tests in tests.__init__
Added pre_delete signal for Topic to remove its corresponding cache
Added proper import of setting (with django.conf) in utils + cleaned TopicCachier
Added test_topic_delete method on TopicCachierTestCase
Moved INSTALLED_APPS feeding with additional apps to app.detective.__init__
Cleaned signals.py
Removed DATABASES setting from settings_tests
Continued testing of utils for topic_cache
Fixed cache issues by adding CACHES setting to settings_tests
Fixed topics' sub models signal binding
Cleaned signals code + added comments