Upped PHPCS standard as far as possible

Improved output escaping & input validation
Add correct sniff repo to travis
Code style: array key spacing
Code style: some more array key spacing
Remove the PHP5.2 problem sniff again
Merge branch 'master' of git://github.com/Yoast/wordpress-seo into PHPCS
Superfluous whitespace
Merge branch 'master' of git://github.com/Yoast/wordpress-seo into PHPCS
Merge branch 'master' of git://github.com/Yoast/wordpress-seo into PHPCS

Conflicts:
	admin/class-config.php
	inc/class-wpseo-options.php
Exclude switch_to_blog sniff
Merge branch 'master' of git://github.com/Yoast/wordpress-seo into PHPCS

Conflicts:
	.travis.yml
	codesniffer.xml
Some more code style clean up
Fix undefined array key notice

Fixes #1319
Merge pull request #1322 from jrfnl/Issue-1319

Fix undefined array key notice, props @jrfnl
Merge branch 'master' of git://github.com/Yoast/wordpress-seo into PHPCS

Conflicts:
	admin/pages/files.php
Double check and remove exclusion of fixed sniffs
Merge pull request #1262 from jrfnl/PHPCS

Upped PHPCS standard as far as possible
Implement proper nonce checking in the bulk editor.
Prevent direct access to XSL file
Merge branch 'master' of https://github.com/Yoast/wordpress-seo