Error when parsing Turtle files with literals that contain double quotes

It seems that the rdfshape client doesn't handle properly Turtle files that contain escaped literals with double quotes. For example something like the following gives a strange error:

```
prefix : <http://example.org/>

:alice :name "\"Alice\"" .
```

The error message is not very helpful and says:

```
Error response from data/info

syntax error in line 3 near '"'
```

