Corrected terminology in comment

Really, really nitpicky change here but ... the comment was referring to the selection rule sets as "declarations", which isn't exactly the correct term. See:

http://nimbupani.com/css-vocabulary.html
http://www.impressivewebs.com/css-terms-definitions/
Merge pull request #1313 from impressivewebs/patch-1

Corrected terminology in comment
Fixed typo in `main.css`
Fix 404 widget script URL

Fix 404 widget script URL to be compatible with HTTPS by replacing
`http://` with `//`. The script hosted by Google is available on both
protocols.
Update CHANGELOG
Merge remote branch 'upstream/master'
moved everything in src and deleted some speciality libs
moved column template to index.html