Refactor array

[bkthomps]

Relates to #67 and #68

Using this as a benchmark for speed:

int i;
int j;
for (i = 0; i < 20000; i++) {
    array me = array_init(10000, sizeof(int));
    for (j = 0; j < 10000; j++) {
        int get = 0xfacade;
        array_set(me, j, &j);
        array_get(&get, me, j);
        assert(get == j);
    }
    array_destroy(me);
}

Over 10 trials, the old array finished in 2.05 seconds while the new array finished in 1.99 seconds. This is 3% faster.

[codecov-commenter]

Codecov Report

Merging #71 into master will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master       #71   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           16        16           
  Lines         2711      2710    -1     
=========================================
- Hits          2711      2710    -1     

Impacted Files	Coverage Δ
src/array.c	100.00% <100.00%> (ø)

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[bkthomps]

Need to check valgrind and update headers.

[bkthomps]

No leaks on valgrind.