message: Update REPL section of CONTRIBUTING.md to reflect changes to `toDate` in v2
diff: @@ -106,8 +106,8 @@ To test a function in REPL, use `babel-node` located in `./node_modules/.bin`:
  > const toDate = require('./src/toDate')
  undefined
  -> toDate('2017-11-17').toString()
  -'Fri Nov 17 2017 00:00:00 GMT+0100 (CET)'
  +> toDate(1392098430000).toString()
  +'Tue Feb 11 2014 01:00:30 GMT-0500 (Eastern Standard Time)'
  >
  ```
  