Install curl

The getting started guide mentions has several examples using curl, so
preinstall curl on the Vagrant box to make the guide easier to follow.
Remove unused font file
Remove highlighting javascript files
Use codeblocks for code
Remove prettify css
Do not underline API doc links
Add robots.txt and sitemap
Cleanup header HTML
Move more javascript into the footer
Import fonts in CSS instead of HTML
Use a description attribute for HTML descriptions
Use new Markdown syntaxes and add SEO descriptions
Update gems to latest versions
Merge pull request #411 from hashicorp/sethvargo/more_website_updates

SEO and latest middleman goodness
Fix small doc mistake
Merge pull request #412 from ErikDubbelboer/website-fix

Fix small doc mistake
CHANGELOG updates
Gofmt
Bump website version
Merge pull request #409 from mark-rushakoff/fuller-vagrantfile

Install curl in vagrant-cluster demo's Vagrantfile