added COBYLA (no REST interface yet)

********* PEOPLE *************
Primary reviewer: @sc932 

Reviewers: @suntzu86 

********* DESCRIPTION **************
Branch Name: denizokt_370_constraints
Ticket(s)/Issue(s): Closes #370 

********* TESTING DONE *************
make test
make style-test
not every domain has a get_constraint_list function. At the 'top' level somewhere it's probably worth checking that domain hasattr get_constraint_list. if it doesn't, raise an exception indicating this is required for cobyla.