Tidied Gemfile.
Whitespace overhaul in blog.css
blog.css renamed to blog.css.scss for Sass pre-processing.
pure-broadstack.css indentation is 2 spaces, not 4.
middleman-bourbon.
blog.css: box-sizing via bourbon.
blog.css: transition via bourbon.
blog.css: inline-block via bourbon.
blog.css: .nav-item Sass nesting.
blog.css: Sass nesting.
body,html min-width decreased to 320px from 400px.

400px was too narrow for iPhones.
Deleted unused pure-menu from pure-broadstack.css
Removed unused .post-category CSS.
Sass constants used in blog.css and pure-broadstack.css
Eliminated generated pure-broadstack.css.
background and padding on code elements, particularly inline.
Envconfig: Environmentally friendly Ruby configuration.