steward new throws an exception

[bradcypert]

~/Projects
❯ steward new
Unhandled exception:
RangeError (index): Invalid value: Valid value range is empty: 0
#0      List.[] (dart:core-patch/growable_array.dart:264:36)
#1      NewCommand.run (file:///Users/bradcypert/.pub-cache/hosted/pub.dev/steward-0.4.0/bin/new.dart:117:22)
#2      CommandExecutor.execute (package:bosun/src/command_executor.dart:11:20)
#3      execute (package:bosun/bosun.dart:13:21)
#4      main (file:///Users/bradcypert/.pub-cache/hosted/pub.dev/steward-0.4.0/bin/steward.dart:6:9)
#5      _delayEntrypointInvocation.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:294:33)
#6      _RawReceivePort._handleMessage (dart:isolate-patch/isolate_patch.dart:189:12)

This is an invalid command (required arguments are missing), but we should provide the user with a meaningful error message. Also this may be a bug in Bosun (https://www.github.com/pyrestudios/bosun)