instructure/canvas-lms — pull request #227 by jbasdf (2012-10-04 19:07:13+00:00)
Title: Fixed style gauntlet regex to allow for negative values such as margin:-18px

A similar commit was made to the source from which this regular expression was derived:
https://github.com/joncalhoun/loofah/commit/ca618fc5f8e6ba146e2d4731c0361368c4b464b2

This change will permit styles with negative values.