Fixed conformance issues with the Udacity style guide.  Specifically:
1.	Fixed color values in main.css to all lower case (#dedede; instead of #DEDEDE;).
2.	Improved alt text for images.
3.	Got rid of type attribute on the links to google fonts used by the page.
4.	Replace single quotation marks with double quotation marks on the links to google fonts used by the page.
5.	Got rid of leading zero on font size (.9em; instead of 0.9em;).
6.	Used new lines to separate several selectors in a declaration.
7.	Fixed section comments in css file.
8.	Got rid of unnecessary rules by targeting broader elements.
9.	Got rid of helper classes.
10.	Improved names for classes where appropriate.
11.	Replace classes by ids where appropriate.