fixed; make statistics start() behave same as ping
fixed; properly handle closing ping dbs
fixed; ping strategy instance start

regression of 4247
test; add ping start test
get tests passing
ping strategy; prevent unnessary safe arnings
fix round robin logic for 2ndaries

when no secondaries exist (at startup), the counter was always
set to NaN. the counter was also getting reset each time defeating
the purpose of round robin.

fixes #746
always return first secondary found

in pickFirstConnectedSecondary

fixes #747
add ReplSet#updateHealth
refactor ReplSet#_validateReplicaset
refactor _handler
line length
refactor to simplify ReplSet health updates
pass missing readPreference w/ server options
fix invalid ref
fixed; honor connectTimeoutMS option
remove incorrect new
add; isObject/isArray,isDate util
fixed; index declaration using objects/arrays from other contexts

closes #754
improve general readability + match style