1. Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
2. Department of Computer Science, University of Toronto, Toronto, Ontario M5S 3H6, Canada
3. IBM Research Zürich, 8803 Rüschlikon, Zürich, Switzerland
4. CIFAR Artificial Intelligence Research Chair, Vector Institute, Toronto, Ontario M5S 1M1, Canada
5. Lebovic Fellow, Canadian Institute for Advanced Research (CIFAR), Toronto, Ontario M5S 1M1, Canada