add reduceRight()

#### V8
```
  Native .reduceRight() vs fast.reduceRight() (3 items)
    ✓  Array::reduceRight() x 5,598,005 ops/sec ±2.14% (92 runs sampled)
    ✓  fast.reduceRight() x 15,059,446 ops/sec ±1.97% (90 runs sampled)
    ✓  underscore.reduceRight() x 4,013,166 ops/sec ±1.85% (88 runs sampled)
    ✓  lodash.reduceRight() x 4,112,906 ops/sec ±1.78% (91 runs sampled)

    Result: fast.js is 169.01% faster than Array::reduceRight().

  Native .reduceRight() vs fast.reduceRight() (10 items)
    ✓  Array::reduceRight() x 2,213,215 ops/sec ±1.92% (87 runs sampled)
    ✓  fast.reduceRight() x 6,042,686 ops/sec ±1.56% (95 runs sampled)
    ✓  underscore.reduceRight() x 1,965,478 ops/sec ±1.87% (89 runs sampled)
    ✓  lodash.reduceRight() x 2,468,101 ops/sec ±1.79% (80 runs sampled)

    Result: fast.js is 173.03% faster than Array::reduceRight().

  Native .reduceRight() vs fast.reduceRight() (1000 items)
    ✓  Array::reduceRight() x 28,038 ops/sec ±1.71% (87 runs sampled)
    ✓  fast.reduceRight() x 72,798 ops/sec ±1.65% (87 runs sampled)
    ✓  underscore.reduceRight() x 28,210 ops/sec ±1.48% (93 runs sampled)
    ✓  lodash.reduceRight() x 48,161 ops/sec ±1.35% (94 runs sampled)

    Result: fast.js is 159.64% faster than Array::reduceRight().

```

#### SpiderMonkey
```
  Native .reduceRight() vs fast.reduceRight() (3 items)
    ✓  Array::reduceRight() x 30,287,360 ops/sec ±0.22% (69 runs sampled)
    ✓  fast.reduceRight() x 32,876,772 ops/sec ±0.39% (68 runs sampled)
    ✓  underscore.reduceRight() x 1,287,249 ops/sec ±3.18% (62 runs sampled)
    ✓  lodash.reduceRight() x 6,765,882 ops/sec ±0.39% (68 runs sampled)

    Result: fast.js is 8.55% faster than Array::reduceRight().

  Native .reduceRight() vs fast.reduceRight() (10 items)
    ✓  Array::reduceRight() x 7,160,762 ops/sec ±0.46% (69 runs sampled)
    ✓  fast.reduceRight() x 7,381,591 ops/sec ±0.40% (67 runs sampled)
    ✓  underscore.reduceRight() x 1,134,680 ops/sec ±3.03% (60 runs sampled)
    ✓  lodash.reduceRight() x 3,072,712 ops/sec ±0.62% (69 runs sampled)

    Result: fast.js is 3.08% faster than Array::reduceRight().

  Native .reduceRight() vs fast.reduceRight() (1000 items)
    ✓  Array::reduceRight() x 70,336 ops/sec ±1.99% (65 runs sampled)
    ✓  fast.reduceRight() x 79,415 ops/sec ±0.34% (69 runs sampled)
    ✓  underscore.reduceRight() x 65,985 ops/sec ±2.21% (63 runs sampled)
    ✓  lodash.reduceRight() x 44,474 ops/sec ±1.53% (67 runs sampled)

    Result: fast.js is 12.91% faster than Array::reduceRight().

```