timing function for Rhino, node, browsers, natively present in JSC
preciseTime() which aim is to provide a double, based on time, precise enough to ensure microseconds, but not as greedy as Java nanoTime in therms of clock.
This precision has been proposed in W3C but is not available yet.
Since JSC offers this natively, the aim of this little script is to normalize this function that specially when it comes to benchmarks or asynchronous queue ordered by execution time, could be all we need.
The node.js version might require microtime. I have not set the dependency since that module has bindings and it might be more problematic to install.
Browsers that do not implement HighResolutionTime will simply return
new Date / 1000 to be consistent with other results.