testWidgets within a `group`

## Steps to Reproduce

1. Create a test file
2. Create a `group` declaration. e.g. `group("MyGroupOfWidgetTests", () { /* Widget Tests here */ });`
3. Put some widget tests within the group
4. Run the tests
5. PROBLEMS:
- Tests are nested an extra level, making them a bit more difficult to read
- One cannot run `testWidgets` tests individually within a group, only the group itself.

## Workarounds

Remove the `group` and move tests to their own file. When tests are out of the group, they are displayed properly and can be run individually.

## Screenshots

## Version info

[✓] IntelliJ IDEA Community Edition (version 2017.2)
• Flutter plugin version 16.0
• Dart plugin version 172.3317.48