update JSONTokener's brief: parse simple json text

[Alanscut]

JSONTokener can parse a simple json text to a simple json object.

[stleary]

What problem does this code solve?
Readme update

Risks
None

Changes to the API?
No

Will this require a new release?
No

Should the documentation be updated?
N/A

Does it break the unit tests?
N/A

Was any code refactored in this commit?
No

Review status
ACCEPTED No comment window needed