have root url redirect to public page
add public site bootstrapping files
simple fix: add empty session to context to satisfy header component

Not ideal…I’d prefer to never set session in the public site.  Consider
the header component call context directly instead of getting it
through props.
add option to pass in route
serve the public site to non-logged in users
fix routes to highlight correct navigation label
Merge pull request #5 from iPlantCollaborativeOpenSource/jchansen/add-back-public-page

Jchansen/add back public page