* query: add --warn-exceptions, dateparser, docs
added --warn-exceptions (like --raise-exceptions/--drop-exceptions, but
lets you pass a warn_func if you want to customize how the exceptions are
handled. By default this creates a logger in main and logs the exception
added dateparser as a fallback if its installed (it's not a strong dependency, but
I mentioned in the docs that it's useful for parsing dates/times)
added docs for query, and a few examples
--output gpx respects the --{drop,warn,raise}--exceptions flags, have
an example of that in the docs as well
