[Hivemind] Add check_comment_date to GitHubCommentExtraction class

[cyri113]

Part of the Github Vectorize (Summary). Please read this document before starting.

Given a PullRequest/Issue id and a date, using the pre-built neo4j connection, query Neo4j to do the previously mentioned checks (see cases / pseudo code), compare the comment counts after a specific date using the equation 1+max([0, (3-days_since_last_comment)]), return comparison flag (True or False).

Tasks

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1. Write a public method check_comment_date in GitHubCommentExtraction
2. Write test cases

The class should have 100% coverage on code climate.

requires #97 .