1. Department of Physics and Astronomy, Pomona College, Claremont, CA 91711, USA
2. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
3. TAPIR, Mailcode 350-17, California Institute of Technology, Pasadena, CA 91125, USA
4. MIT Kavli Institute for Astrophysics & Space Research, Cambridge, MA 02139, USA
5. Department of Astronomy, University of Florida, 211 Bryant Space Sciences Center, Gainesville, FL 32611, USA
6. Department of Physics & Astronomy, University of Victoria, Finnerty Road, Victoria, British Columbia V8P 1A1, Canada
7. Department of Physics & Astronomy, Trent University, 1600 West Bank Drive, Peterborough, Ontario K9J 7B8, Canada
8. Department of Physics and Astronomy, Haverford College, 370 Lancaster Ave, Haverford, PA 19041, USA
9. Department of Physics & Astronomy, Northwestern University, Evanston, IL 60202, USA
10. Center for Interdisciplinary Exploration & Research in Astrophysics (CIERA), Evanston, IL 60202, USA
11. Center for Computational Astrophysics, Flatiron Institute, 162 Fifth Avenue, New York, NY 10010, USA
12. Department of Physics, Center for Astrophysics and Space Sciences, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
13. Kavli Institute for Cosmology & Cavendish Astrophysics, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
14. Hughes Hall College, University of Cambridge, Wollaston Road, Cambridge CB1 2EW, UK
15. Swiss Federal Institute of Technology: ETH Zurich, Department of Physics, Wolfgang-Pauli Strasse 27, CH-8097 Zurich, Switzerland