update readme

README.md

@@ -1,7 +1,7 @@
 High Resolution Time
 =================
 
-High Resolution Time draft spec from webperf
+This specification defines an API that provides the time origin, and current time in sub-millisecond resolution, such that it is not subject to system clock skew or adjustments.
 
 For the latest version, see
   https://w3c.github.io/hr-time/
@@ -10,4 +10,4 @@ See also [Web performance README](https://github.com/w3c/web-performance/blob/gh
 
 Previous versions:
 
-* [Version 2](https://rawgit.com/w3c/hr-time/v2/index.html)
+* Level 1: https://www.w3.org/TR/hr-time-1/