Verify that Chinese stopwords get removed, add some more stopwords if needed

[pypt]

Hey Natalie,

Chinese support (#169) works fine, but it seems like some stopwords are still present in the word cloud:

https://dashboard.mediacloud.org/#query/["北京市"]/[{}]/["2017-6-25"]/["2017-7-9"]/[{"uid":1,"name":"北京市","color":"e14c11"}]

Many terms from the word cloud look like stopwords to me:

Does this Google Translate screenshot make sense? Maybe it would be worth it to introduce some more stopwords by finding more stopword lists and merging them into our current one?

[pypt]

Pushed #173.

[pypt]

@natlungfy, are you sure you've added everything you wanted to the updated list in #173?

I still get "year", "month", "day" in the dashboard word cloud for https://dashboard.mediacloud.org/#query/["北京市"]/[{}]/["2017-6-25"]/["2017-7-9"]/[{"uid":3,"name":"北京市","color":"e14c11"}]:

(By the way, if you add a magic phrase "fixes #issue_number" to your PR's description, this issue will get auto-referenced from the PR and closed once the PR gets merged.)

[pypt]

Deployed, seems to work now!