Add top-level examples to all `Ronin::Exploits::Mixins` modules showing how they are meant to be used

[postmodern]

Every Ronin::Exploits::Mixins:: module should have a top-level example showing how they should be used in an exploit class.

• Ronin::Exploits::Mixins::Binary
• Ronin::Exploits::Mixins::BuildDir
• Ronin::Exploits::Mixins::FileBuilder
• Ronin::Exploits::Mixins::FormatString
• Ronin::Exploits::Mixins::HasPayload
• Ronin::Exploits::Mixins::HasTargets
• Ronin::Exploits::Mixins::HTML
• Ronin::Exploits::Mixins::HTTP
• Ronin::Exploits::Mixins::Loot
• Ronin::Exploits::Mixins::NOPS
• Ronin::Exploits::Mixins::RemoteTCP
• Ronin::Exploits::Mixins::RemoteUDP
• Ronin::Exploits::Mixins::SEH
• Ronin::Exploits::Mixins::StackOverflow
• Ronin::Exploits::Mixins::Text