add new model - stock_data and new lib - data_fetcher
modify seed
fix migrations bug in user and modify migration in create stock data
preliminary implementation of date_updater
add single ticker update
dehydrate code
Merge branch 'master' of https://github.com/COSI236TA/Trade_Assistant
Modify the RuleEngine and DataPool
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Now they are coupled with our database instead of Yahoo Finance API.
Also I added some basic validations for Rule
Decouple our web application from Yahoo Finance API completely
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Now all data request are directed to our database. If there is no such
entry in db, the DataPool will update the database.
Merge pull request #32 from COSI236TA/wenbin

Wenbin