Allow inclusion of request body for JsonParseException

[cowwoc]

As a follow-up to issue #77, please include the entire request body in the exception's message in case of a parsing error. Users will need this extra context to figure out why the parsing error occurred.

[raulraja]

+1 This is a much needed feature since remote services can return anything and the error messages are cryptic as they stand now. It is not always easy to do this from the application since most usages of Jacksons are wrapped in libraries.

[cowtowncoder]

I recommend buffering content first, feeding jackson the byte[]. I don't really see myself working on implementing this feature in core Jackson; but I am always open for contributions.

[cowtowncoder]

So, as can be seen from above, #258 makes it possible to attach content into exception.
Could perhaps consider automation for simple cases where input comes as String or byte[]...