Alt text for logo
Introduction does not make sense out of context
Add a label for search
Style search label as before
Add language
Newline at EOF
Use h2s under h1s
Added good alt text for an image
TODOs for alt texts
Instruct contributors to try to make accessible docs
Added alt text to the elk tutorial images
Merge pull request #720 from ClusterHQ/accessibility-418

Documentation accessibility improvements.

Fixes #418.