Hook up BFGS to rest

********* PEOPLE *************
Primary reviewer: @sc932 

Reviewers: @suntzu86 

********* DESCRIPTION **************
Branch Name: denizokt_285_qei_rest
Ticket(s)/Issue(s): Closes #285 

********* TESTING DONE *************
No, this should not be a constant. (Besides you already have set default number of multistarts to 200).

You need to figure out how to read num_multistarts from the POST request. See for example how we extract num_random_samples. That'll probably be the long term way (I'll create a class MultistartParameters which will have all the multistart stuff in it; to start it'll just be num_multistarts). Right now you'll always override whatever the user specifies, bad.