Altered landing

[harrygfox]

Visual features added:

• slightly slicker transition of styles on the home page header: height and padding alterations with scroll.

Visual glitches fixed:

• url's lacking .html do not display the wrong nav bar (special-case css is imported only in on scenario).
• the nav bar updates better on changing the window size.

Known bugs:

• Site is reliant on refresh: if window is sized down below 992px the onScroll functions still run in spite of the conditionals (see: founder.js).

@sofer @izaaksofer