Removed main element due to spotty support in demo comp Firefox
Added rough draft of 'Introduction to Web Accessibility' README
Added content to README
Added presentation files
Cleaned up links in 'General' section
Cleaned up 'General' section headings
Completed Structuring Content section
Completed HTML document section
Completed Headings section
Completed Images section
Added basic outline for Images section
Renumbered tips
Finished stubbing out Input Labels section
Stubbed out content for links
Stubbed out Color section
Stubbed out Table section
Stubbed out Form Validation section
Stubbed out Keyboard Support section
Stubbed out Navigation section
Stubbed out Fonts section