Remove optional for attributes on input labels

<input> elements that are wrapped in a <label> element have all of the
same functionality and semantics when they don't have a for attribute.
Add a :focus state for menu links
Added smaller image to Grids page
Make inline <code> not wrap on multiple lines

Closes #50
Revert "Remove optional for attributes on input labels"

This reverts commit e5f456fcc7ea6257c602d58485672a056393f0ba.
Merge pull request #95 from ericf/inline-code-nowrap

Make inline <code> not wrap on multiple lines
committed by screwdriver build
Merge branch 'menu-focus-state' of git://github.com/Daniel-Hug/pure-site into menu-focus-state
Add hover/focus state to Pure menu heading item
Clean up main.css' formatting and errors
committed by screwdriver build
Fix button text color regression
Stop cog icon from spinning on Buttons page

Closes #99
Merge pull request #100 from ericf/button-fixes

Button fixes
committed by screwdriver build
Updating master branch just before git squash to merge commits
Fixed whitespace