CONTRIBUTORS.md

Nikhil Jain (UIUC)
    - Improvements in credit-based flow control of CODES dragonfly and torus network models.
    - Addition of direct scheme for setting up dragonfly network topology.
    - Bug reporter for CODES network models.

Xu Yang (IIT)
    - Added support for running multiple application workloads with CODES MPI
      Simulation layer, along with supporting scripts and utilities.