add fast.pluck(), fast.keys() and fast.values()

```
  Native .reduce() plucker vs fast.pluck()
    ✓  Native Array::reduce() plucker x 225,713 ops/sec ±2.11% (87 runs sampled)
    ✓  fast.pluck() x 423,011 ops/sec ±2.01% (90 runs sampled)
    ✓  underscore.pluck() x 397,787 ops/sec ±2.14% (78 runs sampled)
    ✓  lodash.pluck() x 398,084 ops/sec ±1.90% (83 runs sampled)

    Result: fast.js is 87.41% faster than Native Array::reduce() plucker.

  Native Object.keys().map() value extractor vs fast.values()
    ✓  Native Object.keys().map() x 1,097,091 ops/sec ±2.02% (75 runs sampled)
    ✓  fast.values() x 3,059,819 ops/sec ±2.27% (79 runs sampled)
    ✓  underscore.values() x 2,831,113 ops/sec ±1.96% (88 runs sampled)
    ✓  lodash.values() x 2,511,685 ops/sec ±1.88% (88 runs sampled)

    Result: fast.js is 178.90% faster than Native Object.keys().map().

```