Indicate response type in output chart

[SteveDesmond-ca]

As a performance-inclined user, I want to be able to see the types of responses in the output graph, so that I can have a better idea of what my system is doing under load.

Acceptance criteria:

• output graph somehow (translucent stacked bars?) shows at a high level what the responses are like, e.g.
  • 1xx = blue
  • 2xx = green (none by default?)
  • 3xx = yellow
  • 4xx = orange
  • 5xx = red