More function on data_reader including stopword removal, name query.
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Add test case for StemTokenizer
Add prompt and stemmer function to data_reader. Move string processing methods to text.py
Distribution of each prompt
My version of simplified keywords
Add test case
Move data_reader to src. Add class EssayCollection
Function for evaluation
Distance measurement is changed on open_essay to draw some graph
Base method to measure prompt_relevance