Fix nav-bar fluidity. Create scss/sections folder.

The navigation was a <ul> with flexbox properties set on it.
However, it did not behave as expected in mobile browsers. It is
refactored with it's <li> as inline-blocks with relative margins.

A directory, 'scss/sections', has been created to split hold files that
will contain the styling for each unique section. These styles are
currently contained in the single file, '_pages.scss'.