Fix lesson component to better match new site design

[terichadbourne]

• We need to fix the lesson component to better match the new site-wide design that has content centered and wider.
• Change lesson page to have some sort of nav, at least breadcrumbs back to main workshop page if not an identical header to all the other pages
• Need to decide whether we want to continue with a different header on the lesson page from the one on the main page or instead pull in the header component and make them match (benefit of leaving as is is the space saving).

[terichadbourne]

Addressed this as part of PR #59