Jekyll Fix, modify contributor gravatars, boot.backspace.com Blog Post, QCOW -> VHD Blog Post

82017c97f55b0eb22c71069213d4304a67224923: Fix requirement of image_tag in zoomable_image_tag

On a vanilla machine installing the blog via the fork/pull request method, `rake generate` produces the following error out of the box: 
`zoomable_image_tag.rb:20:in <module:Jekyll>': uninitialized constant Jekyll::ImageTag (NameError)`

This is a fix for the missing `ImageTag` plugin that `zoomable_image_tag` plugin requires

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3abdebbaf2e986606f66cba30af41416c2d131fc: Add Mike Metral as contributor

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e8fccf1bda7692c955b9a23ab63a27c5d6439284: Mike Metral blog post on boot.rackspace.com

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63d7b3b65bca3fe30e6c51ab27c082ec6bf9a723: Mike Metral blog post on qcow to vhd conversion