Update ZEffTree with HF variables

Add eSeL, eCOREe9, and e9e25 to the tuples.
Clean up includes in ZEffTree.h

Includes moved inside the #ifdef, and removed TBranch as it is already
included in TTree. iostream is being moved to the .cc
Use stringstreams in ZEffTree.cc instead of cout

Buffering to a stringstream, and then using one cout. This should allow
the code to be more robust when parallelized.