Use https in guide and comment [ci skip]

[yhirano55]

Summary

• Replaced http with https (I checked all replaced url with web browser)
• Fixed Rail Security's url:
  • before http://groups.google.com/group/rubyonrails-security
  • after https://groups.google.com/forum/#!forum/rubyonrails-security

[rails-bot]

r? @kaspth

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