Add lambda character to home page/header.

index.html, _includes/header.html
	-Add the lambda character, which will serve as the site's logo,
	to the home page and header menubar.
Add lambda favicon.

favicon.ico
	-Replace the current favicon (my initials) with a lambda
	character.
Merge branch 'feature/lambda_logo'

_includes/header.html, index.html, favicon.ico
	-Introduce lambda logo for the site.