show build stability next to job name. closes gh-2

This will show the healthReport score for the last 5 builds.
- If the score is 100, display 'Black sun with rays' (U+2600)
- If the score is 80, display 'Cloud' (U+2601)
- Otherwise, display 'Umbrella' (U+2602)

Sure, this isn't as extensive as all the images availble on Jenkins, but
this is just supposed to be a radiator after all.