Faster and less memory intensive Utils::Kernel.Array

**TL;DR** It's a little bit faster, but allocates 1/3 less objects.

```
BENCHMARK:
 
Calculating -------------------------------------
                 old       455 i/100ms
                 new       476 i/100ms
-------------------------------------------------
                 old     4702.9 (±4.0%) i/s -      23660 in   5.039263s
                 new     4800.3 (±6.2%) i/s -      24276 in   5.080260s
 
OBJECTS ALLOCATIONS:
 
Allocations for old:
 sourcefile    sourceline  class  count
-------------  ----------  -----  -----
arraybench.rb           9  Array   3000
 
Allocations for new:
 sourcefile    sourceline  class  count
-------------  ----------  -----  -----
arraybench.rb          20  Array   1000
arraybench.rb          21  Array   1000
```

Source available at: https://gist.github.com/jodosha/c034ac73939aa4c769db