Introducing bitwise ops

All of the tests pass. The two input gate ops are a little slow (`&`, `|`, and `^`), but they are working.

I tried to omit the toString() calls in bitwise, but the Decimal calls to Mod were more expensive. I also tried to capture cases where the two numbers' bits don't overlap (thus replacable with simple addition, one of the values, etc.), but that barely saw a speedup and it added a decent amount of code. It was a lazy function that only checked for base 10, in the hopes of being computationally cheap. Here it is just in case:
```javascript
    function digitsOverlap( x, y ) {
        var xStr = x['toString'](),
            yStr = y['toString'](),
            xEindex = xStr.indexOf( 'e' ) - 3,
            yEindex = yStr.indexOf( 'e' ) - 3;

        if (xEindex < 0) {
            xEindex = xStr.length - 2;
        } else if (x['s'] < 0) {
            --xEindex;
        }
        if (yEindex < 0) {
            yEindex = yStr.length - 2;
        } else if (y['s'] < 0) {
            --yEindex;
        }

        var xLowestDigit = x['e'] - xEindex,
            yLowestDigit = y['e'] - yEindex;

        return (xLowestDigit <= y['e'] + 1) && (yLowestDigit <= x['e'] + 1);
    }
```
I also did not update decimal.js.min.

Feel free to comment on any change you see.
I'd prefer it if `undefined` wasn't used. POWERS_OF_TWO elements can't have a falsey value, so just `if (POWERS_OF_TWO[nNum]) {`.