Modified compositions parsing: Now a topic's proportion has to exceed a topic_threshold for it to be considered as a main topic. An article can have 0 or more compositions. If an article has a main topic, the any other topic whose proportion is within proximity_threshold% of the main topic and > topic_threshold getscounted as a main topic as well. Added tests to test parse_composition(...) and modified the test suite to reflect that change. Also modified the scripts to take into account the fact that we can have more than one main topic now.