Implement a prioritization algorithm to fix loads of bugs in silent nodes.

Hello @eford1, @kylehardgrave, 

Please review the following commits I made in branch 'nick-important-propagation-2'.

7380b7fdae80915f46608274424343b6bb9c9497 (2013-07-24 15:02:35 -0400)
Implement a prioritization algorithm to fix loads of bugs in silent nodes.

a9439093fb5545093389d280347ffcb2cd63d8c9 (2013-07-24 14:39:50 -0400)
add test for bad propagation


R=@eford1
R=@kylehardgrave