Fix a syntax error in flag assignment
It must be up to set_target method to detect the ruby version to be used
within the project to be scanned.

This avoid code setting the target later on to have the ruby version
undetected
Added a spec for Rails engine
Added CVE-2013-1898
Added CVE-2013-1911
Added CVE-2013-1933
Added CVE-2013-1947
Added CVE-2013-1948
Added CVE-2013-2616. Version bumped to 0.58
Added CVE-2013-2617
Added CVE-2013-3221