Various code styling error fixes.
Merge pull request #1101 from dannyvankooten/master

Various code styling error fixes.
Hide PHP_CodeSniffer warnings in Travis.
Add Slack notification
Fix Travis - Slack integration
Encrypt Slack token.
Merge branch 'master' of git://github.com/Yoast/wordpress-seo into Issue-1104-regression-in-var-replacements