Reduce util.inspect depth or make configurable to upper bound serialization expense

[Raynos]

Currently when we fail to serialize a record we will inspect it to a depth of 4 ( https://github.com/uber/logtron/blob/master/transforms/safe-serialize-meta.js#L34 ).

Dependending on the data structure, a depth of 4 can be very expensive, we should probably change it to a depth of 1.