Enquote value in JSonEmitter when it is an infinity float or double

[Rackover]

Stub for fixing https://github.com/aaubry/YamlDotNet/issues/893 Incomplete - missing unit test, and this might not be the best way to handle it either (i haven't looked too much into it). but I guess it's a start? I hope this can be of any help to resolve the issue