Forcing headers: "Server:globaleaks", "X-Content-Type-Options:nosniff"
Forced header: "X-Download-Options:noopen" on Downloaded files
added some mitigation to information leakage on Browser/Proxy Cache
added mitigation to clickjacking attacks on iframes
Merge pull request #114 from globaleaks/security_enforcements

Security enforcements, bump to 0.2.0.20