Accessibility problem with search and comment form

The theme does not have a label for the search form, and the form label for the comment textarea is “display:none”. As a result those using assistive devices like screen readers do not know what these text areas are for.

The following diff fixes the issue.
https://gist.githubusercontent.com/jwenerd/8eda22176964aaa9256e/raw/ad20f2d402d9eda4ae94f8dd13f73a6151a5f9f7/modularity-a11y