Exception information is lost when fields cannot be injected

Specifically, in line 87 of Feather.java:

```
catch (Exception e) {
  throw new FeatherException(String.format("Can't inject field %s in %s", field.getName(), target.getClass().getName()));
}
```

The caught exception is discarded. It would be preferable to set the caught exception as the cause by passing it in as the second argument to FeatherException.
