remove some cruft from README

README.md

@@ -104,7 +104,7 @@ _Do not look below this line_
   sessions are then presented to the rider who may approve them
   as-is - perhaps involving other data collection as well ("perceived
   effort" or "which bike setup was this" or ...) - or chop them up
-  using information thy have but the computer doesn't
+  using information they have but that the computer doesn't
 
 in theory we don't even need draft sessions and we could have the
 rider create sessions from the calendar page. However, that's a GET
@@ -119,38 +119,10 @@ we show time spent in HR zones ...
 
 ----
 
-time axis wants to show ticks which are at least (portalWidth/4)
-pixels apart, and choose the smallest of the following time intervals
-which are greater than that width
+start and end marks can be drag targets but we also need to know where
+they are when they're not being dragged
 
-1 second
-5 seconds
-15 seconds
-30 seconds
-60 seconds
-5 minutes
-15 minutes
-1 hour
-3 hours
-6 hours
-24 hours
-
-if the full width is 240 seconds, show a tick every 60 second
-if the full width is 20 seconds, show a tick every 5 seconds
-
-if the width grows past 20 seconds, the distance between points shrinks
-and therefore we put ticks less often
-
-if width <= 4 * 5, 5 second tick
-if width <= 4 * 15, 15 second tick
-etc ...
-
-to convert time to pixels, multiply by portalWidth / duration
-
-
-
-
-portalWidth / duration
+selectedRange start, duration