Eliu gh 358 fix kwarg handling in combined example

********* PEOPLE *************
Primary reviewer: @sc932 

Reviewers: @ Feriority

********* DESCRIPTION **************
Branch Name: eliu_gh_358_fix_kwarg_handling_in_combined_example
Ticket(s)/Issue(s): Closes #358

    1. fixing bug where combined_example drops kwargs if the more specific kwargs aren't set
    2. adding kwargs to mean_var in moe_examples


********* TESTING DONE *************
make test