Support of changing lvl @ runtime
add support for changing levels at runtime (#38) this allows configuring zapsentry with other zap.LevelEnabler implmentations (namely, zap.AtomicLevel) which makes it easy to change Sentry reporting threshold at runtime, without re–creating logger and/or core objects since various zap.*Level consts are also LevelEnablers, this change is backwards compatible Co-authored-by: Alexey Surikov <[email protected]>