Add .site-wrapper class to #wrapper div
Add .site-header class to #header div
Add .site-main class to #main div
Add .content-wrapper class to #container div
Add .branding class to #branding div
Add .site-title class to #blog-title
Add class .tagline to #blog-description div
Add class .site-content to #content div
Add class .site-footer to #footer
Add css classes to widget areas
Merge pull request #66 from ThematicTheme/feature/add-css-classes

Close #50