Various code styling error fixes.
Added check if cat_name is set when replacing title variables so %%category%% get's properly replaced on category archive pages.
Fixes #1106.
Merge branch 'master' of github.com:Yoast/wordpress-seo
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 Meta-snippet-help