only fetch value once on serialization and cache the varint encoding …

[abrandoned]

…for most common cases (< 1024)

adding a cache of varint fields for any varint < 1024 for now (may make configurable in the future), runs it on load and uses the cached values instead of calculating

https://gist.github.com/abrandoned/044cf200037ff7885572

about 100% increase in encoding time of varints under jruby when varint is > 128; < 128 10%