build error when syntax error in file

Given a file e.g. **foobar.js**, literally containing a syntax error such as:

``` js
)
```

or

``` js
+
```

or

``` js
delete
```

or etc.

causes `component build` to freak out:

```
> component build
       build : resolved in 25ms

       error : undefined
```

with very little explanation about what's going on.
