merging PR Chaosthebot#518: Ignore neutral reviews

Chaosthebot#518: Ignore neutral reviews

Description:
Currently a neutral review (the default when you use "add single comment" instead of "start a review") will override an approval. This PR makes chaosbot ignore netural reviews, so they don't override positive reviews. A positive review can still be overriden with a negative review (which currently is treated the same as no review at all).

:white_check_mark: PR passed with a vote of 7 for and 0 against, a weighted total of 7.0 and a threshold of 6.5, and a current meritocracy review.

Vote record:
@PlasmaPower: 1
@Swizz: 1
@andrewda: 1
@JustynC7: 1
@mark-i-m: 1
@phil-r: 1
@rhengles: 1

github_api/voting.py

@@ -107,7 +107,8 @@ def get_pr_review_reactions(api, urn, pr):
         user = review["user"]["login"]
         is_current = review["commit_id"] == pr["head"]["sha"]
         vote = parse_review_for_vote(state)
-        yield user, is_current, vote
+        if vote != 0:
+            yield user, is_current, vote
 
 
 def get_vote_weight(api, username, contributors):