Readers fail to parse escaped characters

[Sparika]

Related to #4 , it appears that both turtle and ntriples reader are not able to process literal containing escaped character with a \.

@base <file> .
_:138df0aa-cf7c-4457-5377-26957f4df295 <number> "1571909016132" ;
        <escape> "\"escaped\"string" ;

Errors are the following and disappear when removing the line containing escaped characters.

[2019-11-21T10:26:17Z ERROR program] Invalid token while reading Turtle triples.

[2019-11-21T10:20:35Z ERROR program] Error while parsing NTriples syntax.

Any idea as to where to look ?