Introduce Inactive Specs

* specs.js: Remove symbol, symbolsType, overflowFragment data types
* specs.js: Remove css-overflow-3, css-gcpm-3, css-sizing-3, css-counter-styles-3, css-display-3, css3-tables, css-content-3, css3-marquee, css3-hyperlinks, css-page-template-1, css-containment, css-page-floats, css-module, css-speech-1, css-color-correction-1, css-preslev-1, css-size-adjust, css-snappoints-1, css-regions-1, css-ruby-1, css-line-grid-1, selectors-nonelement, css-pseudo-4, books, figures, becss, view-mode, css2 specs
Remove JSHint's onevar rule

This rule no longer works.
Update README.md about Support Browsers