HTML 5 compatibility fixes

[nycdotnet]

• Added HTML5 DOCTYPE tags and meta tags in all but email.html (which I am assuming is intentionally an HTML fragment). The DOCTYPE combined with the x-ua-compatible meta tag is required to get the pages to render correctly in IE in corporate environments (like mine, and I'm assuming other PS customers) that assume quirks mode should be the default on intranet sites (which includes localhost) unless these tags are present.
• Also fixed un-escaped ampersand in index.html.

Warning: this may cause inconsistencies with line numbers such as in clip 6 of module 3 at :25 seconds where you say "around line 31" and now it's around line 35. (Hopefully any developer for whom your course is appropriate will be able to work around this).

[ryanmurakami]

Thanks Steve! I think the line number change should be fine.