Telemetry experiments now in nightly

[Benjamin Smedberg]

Telemetry experiments is enabled as of this morning's Nightly.

Our first experiment is already live: it reorders the tiles in 
about:newtab so that the most-frecent tile is in the center instead of 
the top-left. The experiment should deploy to 25% of nightly users for a 
5-day period from now through 15-May. Users who have DOM inspector or 
tree-style-tabs active will not receive this experiment. This experiment 
is mainly deployed to check that the experiment system and experiment 
conditions are working correctly. To see a list of current and past 
experiments, visit https://telemetry-experiment.cdn.mozilla.net/

If you have experiments that you'd like to run, either now on nightly or 
on other channels as this rides the trains, please email me or file a 
bug in Firefox:General and cc me.

Questions/comments/replies to firefox-dev please.

--BDS