Make ./examples/run_examples.sh fail loudly (#588)

* Make ./examples/run_examples.sh loudly fail

If you do:

```
./examples/run_examples.sh
rm src/types.rs
./examples/run_examples.sh
```

The second run will succeed even though the compilation failed. Fix this
by making the script fail if one of the steps fail.

* and set +e before the for