fix port to be 4200 in README
fix port to be 4200 in README

josemarluedke/ember-cli-fastboot,kratiahuja/ember-cli-fastboot,josemarluedke/ember-cli-fastboot,tildeio/ember-cli-fastboot,ember-fastboot/ember-cli-fastboot,tildeio/ember-cli-fastboot,ember-fastboot/ember-cli-fastboot,kratiahuja/ember-cli-fastboot