Add support for sending arbitrary context data

[joshuap]

In Ruby we can do:

Honeybadger.context({
  foo: 'bar'
})

and/or:

Honeybadger.notify(error, context: {bar: 'baz'})

The first is registered globally and the second is registered only for that exception and merged into the global context.

The context object itself is a map which is sent in the JSON payload for the error under payload['request']['context'].

[JoshAshby]

In case anyone else is looking for how to do this (as of 1.1.0), I ended up doing:

io.honeybadger.reporter.dto.Context context = new io.honeybadger.reporter.dto.Context();
context.put("thing", "data");
io.honeybadger.reporter.dto.Request request = new io.honeybadger.reporter.dto.Request(context, null, null, null, null);
reporter.reportError(exception, request); // reporter is an instance of HoneybadgerReporter

Which isn't too pretty but works.