v3.0.0

• Added 'no-js' class to HTML element to help with progressive enhancement
• Added meta theme-color tag
• Added minor accessibility improvements
• Added picture element to media.html example file
• Changed nav toggle element to button
• Changed "View Source" and "Copy Source" actions to button elements
• Cleaned up spacing and comment wording in functions.php
• Cleaned up sg-scripts.js
• Cleaned up sg-style.css
• Removed global form navigation
• Removed example of fieldset with large amount of text
• Removed code-prettify (prettyprint) styles
• Reworked listMarkupAsOptions function into listMarkupAsListItems function
• Reworked layout template and styles to be more responsive
• Updated README.md
• Updated media query breakpoints
• Updated wording in "Getting Started" section
• Updated meta viewport tag
• Updated font stack markup and styling
• Updated color swatch markup and styling
• Updated JavaScript syntax highlighter to prism.js