use our internal apply helpers everywhere

Thanks @jdalton for the suggestion. Provides a small but significant speed boost in `.bind()`, `.partial()` and `.partialConstructor()`. We still get our asses kicked by SpiderMonkey for prebound functions, but it's still faster than before:

#### V8
```
  Native .bind() vs fast.bind()
    ✓  Function::bind() x 832,970 ops/sec ±1.44% (85 runs sampled)
    ✓  fast.bind() x 7,142,465 ops/sec ±0.91% (93 runs sampled)
    ✓  fast.bind() v0.0.2 x 6,376,371 ops/sec ±1.14% (88 runs sampled)
    ✓  underscore.bind() x 528,686 ops/sec ±1.57% (80 runs sampled)
    ✓  lodash.bind() x 349,213 ops/sec ±2.10% (80 runs sampled)

    Result: fast.js is 757.47% faster than Function::bind().

  Native .bind() vs fast.bind() with prebound functions
    ✓  Function::bind() x 4,596,421 ops/sec ±1.05% (93 runs sampled)
    ✓  fast.bind() x 19,187,335 ops/sec ±0.97% (87 runs sampled)
    ✓  fast.bind() v0.0.2 x 13,930,265 ops/sec ±0.94% (89 runs sampled)
    ✓  underscore.bind() x 4,562,916 ops/sec ±0.95% (86 runs sampled)
    ✓  lodash.bind() x 4,860,192 ops/sec ±1.17% (87 runs sampled)

    Result: fast.js is 317.44% faster than Function::bind().

  Native .bind() vs fast.partial()
    ✓  Function::bind() x 841,061 ops/sec ±1.83% (80 runs sampled)
    ✓  fast.partial() x 8,674,420 ops/sec ±1.54% (93 runs sampled)
    ✓  fast.partial() v0.0.2 x 7,056,606 ops/sec ±1.43% (87 runs sampled)
    ✓  fast.partial() v0.0.0 x 6,806,520 ops/sec ±1.31% (87 runs sampled)
    ✓  underscore.partial() x 1,629,855 ops/sec ±1.49% (90 runs sampled)
    ✓  lodash.partial() x 329,820 ops/sec ±2.75% (69 runs sampled)

    Result: fast.js is 931.37% faster than Function::bind().

  Native .bind() vs fast.partial() with prebound functions
    ✓  Function::bind() x 4,362,196 ops/sec ±1.54% (91 runs sampled)
    ✓  fast.partial() x 18,008,835 ops/sec ±1.37% (73 runs sampled)
    ✓  fast.partial() v0.0.2 x 13,511,525 ops/sec ±1.40% (82 runs sampled)
    ✓  fast.partial() v0.0.0 x 13,379,174 ops/sec ±1.53% (78 runs sampled)
    ✓  underscore.partial() x 6,610,677 ops/sec ±1.25% (91 runs sampled)
    ✓  lodash.partial() x 4,630,166 ops/sec ±1.36% (87 runs sampled)

    Result: fast.js is 312.84% faster than Function::bind().

```
#### SpiderMonkey
```
  Native .bind() vs fast.bind()
    ✓  Function::bind() x 1,052,708 ops/sec ±3.17% (52 runs sampled)
    ✓  fast.bind() x 1,998,159 ops/sec ±2.90% (58 runs sampled)
    ✓  fast.bind() v0.0.2 x 850,026 ops/sec ±2.40% (63 runs sampled)
    ✓  underscore.bind() x 491,642 ops/sec ±3.26% (56 runs sampled)
    ✓  lodash.bind() x 255,096 ops/sec ±2.15% (62 runs sampled)

    Result: fast.js is 89.81% faster than Function::bind().

  Native .bind() vs fast.bind() with prebound functions
    ✓  Function::bind() x 75,606,163 ops/sec ±0.51% (68 runs sampled)
    ✓  fast.bind() x 9,952,095 ops/sec ±0.55% (67 runs sampled)
    ✓  fast.bind() v0.0.2 x 4,535,786 ops/sec ±1.13% (66 runs sampled)
    ✓  underscore.bind() x 74,498,853 ops/sec ±0.59% (67 runs sampled)
    ✓  lodash.bind() x 1,680,624 ops/sec ±2.38% (64 runs sampled)

    Result: fast.js is 86.84% slower than Function::bind().

  Native .bind() vs fast.partial()
    ✓  Function::bind() x 1,105,650 ops/sec ±3.08% (52 runs sampled)
    ✓  fast.partial() x 2,245,123 ops/sec ±3.01% (60 runs sampled)
    ✓  fast.partial() v0.0.2 x 917,150 ops/sec ±2.15% (64 runs sampled)
    ✓  fast.partial() v0.0.0 x 916,274 ops/sec ±2.28% (62 runs sampled)
    ✓  underscore.partial() x 818,945 ops/sec ±1.93% (60 runs sampled)
    ✓  lodash.partial() x 263,751 ops/sec ±2.30% (62 runs sampled)

    Result: fast.js is 103.06% faster than Function::bind().

  Native .bind() vs fast.partial() with prebound functions
    ✓  Function::bind() x 78,707,103 ops/sec ±0.33% (69 runs sampled)
    ✓  fast.partial() x 9,642,861 ops/sec ±0.43% (66 runs sampled)
    ✓  fast.partial() v0.0.2 x 4,203,013 ops/sec ±1.27% (40 runs sampled)
    ✓  fast.partial() v0.0.0 x 4,162,810 ops/sec ±0.82% (67 runs sampled)
    ✓  underscore.partial() x 3,163,519 ops/sec ±0.46% (68 runs sampled)
    ✓  lodash.partial() x 1,593,738 ops/sec ±2.59% (61 runs sampled)

    Result: fast.js is 87.75% slower than Function::bind().

```

fixes #49 
> I've taken issue with your priority of micro-opts  and proven that the supposed wins are negligible and overshadowed by more substantial perf work.

They're *not* a priority, they are low hanging fruit. Obviously there are going to be greater wins in some cases with more fundamental algorithm changes, but we haven't got there yet (this project has only been around for a week). One of the most basic things you can do to speed up a program is to eliminate redundant work, and that's all we're doing here. We're not even jumping through hoops for it, it's simple stuff. It is *you* who is fixated on it.

> I haven't used bluebird or done a deep review of its code.

Ah sorry, I must have misinterpreted a tweet I saw.

> Don't forget to apply ice to that burn.

I literally loled. I'm stepping away (or trying to) because we're not going to come to agreement in this case, not because you have somehow won at internetting :grinning: