Include error message detail in request exception.

Not sure if a multiline exception is the right way to go here, but it'd be nice to see the error when the exception is thrown.

Before:

    IntuitRequestException: Required param missing, need to supply the required value for the API
    [Stack Trace]

After:

    IntuitRequestException: Required param missing, need to supply the required value for the API:
        Required parameter Line.DetailType is missing in the request
    [Stack Trace]

Other options:
Use the detail as the error message.
Other based on message type.

Let me know what you think.