fix #185 stagehand integration

## Stagehand

Stagehand in Sublime Text works as follows:

1. Select *Dart: Stagehand* from the command palette
2. Select type of template (quick list, top)
3. Select target directory (input panel, bottom)

In (3), you can get completions by pressing <kbd>Tab</kbd> or <kbd>Shift</kbd>+<kbd>Tab</kbd>.

The chosen directory will be created if it doesn't exist.