Include tract info in Block Group header box "name" area

[JoeGermuska]

As correctly noted in UserVoice #344, our block group profile pages don't provide the key contextual information about which tract they're in, leaving people to decode the geoid to know the tract.

Ideas:

• Blow out the "name" value to include the tract. Cons: much longer than all other geo names, would probably have bad design consequences
• Special case: when rendering the header box, recognize block groups (sumlevel 150) and extract the tract from the GeoID and add it in a subsidiary type treatment near the main "name"
• Include the tract in the list of containing geographies (where it arguably should be anyway) and see if that's an adequate solution.

[JoeGermuska]

@ryanpitts do you still think about this? thinking about using this as a warm-up exercise for the new student developers.