Merge pull request #247 from za/master

Update plugin_vulns.xml: SQL injection fixed in events-calendar version ...
Fix #208 - Fixed vulnerable plugins still appear in the results
WpItems::Detectable#passive_detection Complexity Reduced
Handle when there are 2 headers of the same name
Little refactoring
Added security headers
Missunderstood known_headers array, removed security headers
Added SWFUpload Content Spoofing in 3.5.2 see issue #243
fix typo at wp_versions.xml comment: verions->versions