Update normalize.css to v3.0.0.
Update modernizr to v2.7.1.
Losslessly compress images.

Before: 89,5 KB (91.747 bytes)
After:  87,4 KB (89.573 bytes)
Merge pull request #2128 from XhmikosR/compress-images
Update history to reflect merge of #2128 [ci skip]
Merge pull request #2126 from XhmikosR/normalize.css
Update history to reflect merge of #2126 [ci skip]
Initialize each command in its own class so we can be *magical*.
Have a list of blessed gems to require and load.
Merge pull request #2143 from jekyll/fix-cli
Update history to reflect merge of #2143 [ci skip]
Merge pull request #2129 from XhmikosR/modernizr
Update history to reflect merge of #2129 [ci skip]
Remove modernizr and use html5shiv.js directly.

Also add respond.js so that media queries work in older IE too.