Update qs NPM dependency [help wanted]

[dr-dimitru]

Shout out to all developers, help wanted to update qs NPM package dependency to the latest release (as time of posting v6.9.1);

Using any version newer than v6.5.2 won't pass auto-tests.

Failed tests on meteor@1.9:

• Client - Router - setParams - preserve query strings

This is not today's discovery, I've trying to find an issue during last year. Hope someone from community worked directly with qs package and would suggest or send a PR to fix current issue. Similar to #74