Build testing and accuracy, performance benchmark framework

[Aman Mangal]

Previous work -

• https://github.com/dgryski/trifles/tree/master/cachetest
• https://github.com/dgraph-io/badger/tree/master/ristretto

[Ben Manes]

Simulator:
https://github.com/ben-manes/caffeine/wiki/Simulator

[Ben Manes]

Golang port of Caffeine’s benchmark
https://github.com/dgraph-io/benchmarks/blob/master/cachebench/cache_bench_test.go

[Karl McGuire]

The benchmarking framework resides in the bench folder (for now).

Things to be added in order of priority, as per @ben-manes' useful notes on this subject:

1. Mixed get/set workloads
2. Zipf key accesses
3. Sequential cost of insert / eviction
4. Trace formats: CORDA, LIRS, ARC

I'll look into Java's trace simulator and see if it will be easier to go-bind or loosely structure our implementation off of it.