use new hostname in readme
use new hostname in readme

- delphi.cmu.edu instead of delphi.midas.cs.cmu.edu
- code still needs to be updated

cmu-delphi/delphi-epidata,cmu-delphi/delphi-epidata,cmu-delphi/delphi-epidata,cmu-delphi/delphi-epidata,cmu-delphi/delphi-epidata,cmu-delphi/delphi-epidata