Add a note in changelog to clear the browser's cache

[d-rez]

At first I thought the newest release was bugged after you've changed how data series' - filtering works now (ctrl-click didn't work, series didn't appear again after hiding them).

Then I remembered that browsers cache all static files. The file has changed but for some reason my apache was still reporting it as 304 Not Modified.

Clearing browser's cache helped and all works now. Maybe it's a good idea to add such a note?

[torkelo]

Yes, for the next release I will try to fix this (#418)

[torkelo]

But thanks for reporting this. As soon as I have gone trough some of the more high prio pull requests I will fix 418 so it is done before the next release.

[d-rez]

Ooo seems like I deleted my previous comment. Anyway, sorry for creating a duplicate. I swear I've checked the issues list but somehow haven't noticed that it's already been reported (bad deduction skills I guess). Thanks! :)