ammonite.ops.read! is really slow

``` scala
ammonite.ops.read! jsonFile
```

seems about an order of magnitude slower than

``` scala
java.nio.file.Files.readAllBytes(java.nio.file.Paths.get(file.toString))
```

This should not be the case. We should fix whatever is making it slow, or override it so it just forwards to `readAllBytes` 
