whitespace cleanup on _includes/searchbox_partial.html
create partial for the <nav> element
add "header-element-margin" class to "searchbox" element sitewide
add "navigation_partial.html" partial file to all layout templates
update desktop and tablet styles

copy all header-based styles from desktop over to laptop.  add 'header-element-margin' class to nav and search box, which pushes them over to the right and required changes to 'searchbox-style' class. add rounded corners to searchbox.
add tablet based styles based on the previous commit (1996578...)
remove all padding from the "show-menu" Sass mixin
push both production and development copies of styles.css to GitHub