Added functionality for deleting old hashtags

Hashtags with a value of one will automatically be removed every hour.  Tweets that are older than 24 hours will be continuously deleted.  The count of hashtags updates as the tweets are added and removed.
Created dotenv file with api keys and db user/password
Merge pull request #5 from rjbernaldo/connect-to-mongodb

Added functionality for deleting old hashtags
Merge pull request #6 from rjbernaldo/anonymize_keys

Anonymize keys
added procfile
Merge pull request #7 from rjbernaldo/heroku_optimization

[@mameneses] looks good to me
changed procfile
changed procfile again to web: npm start
Merge pull request #8 from rjbernaldo/troubleshoot_heroku

Troubleshoot heroku
Fixed merge conflict