invalid syntax through inverted comma in README example

[PeterNerlich]

Saw this by chance, there is an unescaped inverted comma in the usage example with curl:

curl -H 'Content-Type application/json' -X POST -d '{"doc":"Whether you think that you can, or that you can't, you are usually right."}' http://localhost:5000/index_text

This should be

curl -H 'Content-Type application/json' -X POST -d "{\"doc\":\"Whether you think that you can, or that you can't, you are usually right.\"}" http://localhost:5000/index_text

to work properly. I made a quick search for other options, but this seems to be the easiest 😅