Schleimer-Segerman makers' mark

This is the logo my collaborator [Saul Schleimer](http://homepages.warwick.ac.uk/~masgar/) and I add onto our models. It is a 2-dimensional stylised picture of the [Whitehead link](http://en.wikipedia.org/wiki/Whitehead_link), a key example from our research area, 3-dimensional geometry and topology. It also resembles our initials!