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
this is pretty non-intuitive and could definitely use some explaining in docstrings.

i think it'd also be possible to access ```[i % dim]``` looping over all points. although that probably goes against the philosophy of the repeated domain class. still if that is substantially better behaved for cobyla that may be worthwhile

I see what you mean about the x >= 0 thing. i think you're right. Have you tested that the constrained part works (i can't remember if the basic optimization unit tests have constrained cases)