L-BFGS-B Implementation

Very rough at the moment. Uploaded for potential comments/suggestions.

********* PEOPLE *************
Primary reviewer: @sc932 

Reviewers: @suntzu86 

********* DESCRIPTION **************
Branch Name: denizokt_228_implement_LBFGSB
Ticket(s)/Issue(s): Closes #228 

********* TESTING DONE *************
make test
Okay for some reason nothing breaks anymore when I set DOMAIN_ERROR to 0.0... 
I just removed it and it works fine.