gradlew isn't executable (bummer on unix systems)

The `gradlew` script was checked in with non-executable permissions, which means unix users can't use it out-of-the-box. To fix:

```
git add --chmod=+x -- gradlew
git commit -m "make gradlew executable"
```

Only happens when a repo is started by a windows user. It will stay fixed even after updating the gradlew wrapper on a windows machine in the future. You can run the commands above on a windows or unix machine.

Inspect the checked-in gradlew file and its Unix executable permissions. Use the git add --chmod=+x command described in the issue, then verify that the executable bit is preserved; done means Unix users can run gradlew out of the box and future wrapper updates retain that permission.

Written by the indexing model from the issue text.