Decouple logic between stackoverflow and display modules

[briancohan]

Organize stackoverflow module so that the Stackoverflow object will keep track of which question its displaying and provide the markdown-rendered content for the display module. The SO module should also provide the rendering for --no-display mode.

The display module should be able to handle the Stackoverflow object and ask it what to render in the main view and side bar. Similarly, there should be a traceback module that the display module will query as well.