Update Readme. Fixes Issue #240

[johnjaylward]

Update Readme to note that the parser allows some invalid JSON text while the generator never should.

[theCapypara]

It should be RFC7159, not RFC7169

[johnjaylward]

thanks fixed

[stleary]

What problem does this code solve?
This is a change to the README documentation. Normally it would just be committed, but in this case a few days will be included for review, in case anyone has comments. The project diverges from the specs in that when parsing strings, control chars other than '\n', '\r', and binary 0 are allowed. The team believes that the benefit of following the spec exactly does not outweigh the potential cost of breaking existing applications.

Changes to the API?
No.

Will this require a new release?
This change will be rolled into the next release, which is expected in June 2016 timeframe.

Should the documentation be updated?
Yes, this is the doc change (README only).

Change to unit tests?
A new unit test is added, which documents the existing behavior. See stleary/JSON-Java-unit-test#50