Added Buffer & Array equality check and added includeDiffOnDataEquali…

[bontscho]

PR for #38

I kept the code I added as close to the code style of the existing code. To be a non-breaking update, I added the option includeDiffOnDataEquality and defaulted it to true. This allows for setting it to false if the diff is not wanted on strict equality.

For speed comparison, I put together a small benchmark script with the following results:

# Same Buffers ( comparing 1a.png with 1a.png)
$ node benchmark.js 1a 1a
before # Buffer(includeDiffOnDataEquality=true) x 256 ops/sec ±1.62% (84 runs sampled)
after # Buffer(includeDiffOnDataEquality=true) x 791 ops/sec ±2.16% (84 runs sampled)
before # Buffer(includeDiffOnDataEquality=false) x 254 ops/sec ±1.91% (83 runs sampled)
after # Buffer(includeDiffOnDataEquality=false) x 27,263 ops/sec ±2.59% (84 runs sampled)
before # identical Arrays (includeDiffOnDataEquality=false) x 55.60 ops/sec ±2.10% (57 runs sampled)
after # identical Arrays (includeDiffOnDataEquality=false) x 3,171 ops/sec ±2.79% (78 runs sampled)
before # identical Arrays (includeDiffOnDataEquality=true) x 55.62 ops/sec ±2.42% (63 runs sampled)
after # identical Arrays (includeDiffOnDataEquality=true) x 148 ops/sec ±1.80% (74 runs sampled)
before # different Arrays x 10.56 ops/sec ±3.22% (30 runs sampled)
after # different Arrays x 15.75 ops/sec ±2.23% (43 runs sampled)
Fastest is after # Buffer(includeDiffOnDataEquality=false)

# Different Buffers ( comparing 1a.png with 1b.png)
$ node benchmark.js 1a 1b
before # Buffer(includeDiffOnDataEquality=true) x 244 ops/sec ±2.06% (80 runs sampled)
after # Buffer(includeDiffOnDataEquality=true) x 250 ops/sec ±1.61% (83 runs sampled)
before # Buffer(includeDiffOnDataEquality=false) x 249 ops/sec ±1.81% (82 runs sampled)
after # Buffer(includeDiffOnDataEquality=false) x 246 ops/sec ±2.05% (81 runs sampled)
before # identical Arrays (includeDiffOnDataEquality=false) x 53.53 ops/sec ±1.91% (68 runs sampled)
after # identical Arrays (includeDiffOnDataEquality=false) x 2,879 ops/sec ±8.06% (71 runs sampled)
before # identical Arrays (includeDiffOnDataEquality=true) x 52.71 ops/sec ±2.40% (67 runs sampled)
after # identical Arrays (includeDiffOnDataEquality=true) x 149 ops/sec ±1.90% (74 runs sampled)
before # different Arrays x 10.48 ops/sec ±3.79% (30 runs sampled)
after # different Arrays x 14.74 ops/sec ±3.92% (40 runs sampled)
Fastest is after # identical Arrays (includeDiffOnDataEquality=false)

Looking forward to your feedback