Jialei gh270 connect cuda ei to optimization algorithm

********* PEOPLE *************
Primary reviewer: @suntzu86

Reviewers: @sc932

********* DESCRIPTION **************
Branch Name: jialei_gh270_connect_cudaEI_to_optimization_algorithm
Ticket(s)/Issue(s): Closes #270 

********* TESTING DONE *************
make test
cpplint.py
can you put the double backticks around fcn and file names? so:
```
``ComputeOptimalPointsToSample``
``gpp_math.cpp``
```
here & elsewhere