optimize the number of hover setState() invocations
optimize the number of hover setState() invocations

optimize the number of setState() invocations
- hover events happen in rapid succession
- setState() is NOT guaranteed to be synchronous
- utilize our own separate lastSetHoveredStudent setting to:
* KEY: reduce the number of setState() invocations by 50%

KevinAst/GeekU,KevinAst/GeekU