Revert "pre-define map capacities" (#200)
Revert "pre-define map capacities" (#200)

Reverts honeycombio/libhoney-go#197

The solution here adds additional locks and lacks configurability, and
we'd like to first try a different path. A combination of vacation, time
zones, and a weekend caused our wires to get crossed.
honeycombio/libhoney-go