Points "slide" at small time-ranges / support for micro and nano-seconds

You can see the problem I'd like to fix in the [wind example](http://software.es.net/react-timeseries-charts/#/example/wind) (which does not set a minDuration) if you zoom in as far as possible. The points will start to "slide around" without updating the axis values if you keep zooming when the chart gets to only being about 1 second wide.

This is a common issue for us when examining micro-processor level events. We frequently zoom in on these slices from a batched overview of hours or days of data, so artificially tweaking their timestamps isn't a great option.

I think this issue is just because real JS dates don't support micro or nano resolution and Pond is using real dates. d3 scales and formats have had some support for microseconds added the last couple years. format just via slicing off the microsecond value before running the rest of the formatter and adding it back later. This is similar to how [other projects do it](https://github.com/jcgertig/nano-date#readme).

I haven't tested d3 scales with microseconds, but the [most recent commit to d3-scale/time](https://github.com/d3/d3-scale/commit/07e829cfe4c3cff6956ef7d685806cb44598dfda) implies it works at least slightly better than the performance in the wind example.

This issue might belong over at Pond, since it seems most of the work would be allowing TimeSeries and TimeEvents to take strings and/or 16 digit numbers in addition to Dates.