Hover states, HTML and CSS trimming

[SaFrMo]

• Added larger hit areas and hover states per Add hover states and larger hitboxes #23
• Removed deprecated <center> elements
• Trimmed CSS that duplicates browser defaults, restructured some CSS to deal with future additions more easily
• Standardized class names

Hoverstates look like this:

There's a good bit of change in the CSS so I'm happy to review if there are any conflicts, but I didn't see any when merging into the existing version or my PR at #18 . Let me know anything else that looks off - thanks!

[everestpipkin]

Looks great- thank you!