Minor modification to various classes

Change log:
_main.scss
	added base-font-family variable to html tag
	added position: relative

_reset.scss
	removed force cursor to text on all input

_shared.scss
	removed hr margin rules
Minor changes to classes

Change log:
mixins
	added text-shadow mixin

shared
	altered margin-bottom value

nav
	updated all sub-classes to properly extend .nav base class