Add support for deep property checking

[mitchellsimoens]

For issue #4

Adds the deep modifier as in chai. You can use dot or bracket notation for objects and arrays.

[mitchellsimoens]

@dongryphon looks like the yarn install in the travis run is borked

[dongryphon]

Thanks for the heads up - I'll take a look at this tonight (hopefully)

[dongryphon]

Could be a good deal simpler / perfier in this form:

    let obj = object;
    let prop = property;

    if (deep) {
        let parts = property.split(/.../);
        prop = parts.pop();

        for (let part of parts) {
            if (!obj) {
                return false;
            }
            obj = obj[part]; // ish
        }
    }

    // pretty much as before using obj / prop instead of object / property

?

[dongryphon]

Looks like the tests are running now but there are some failures

[mitchellsimoens]

Odd, new failures do no appear with node v6 but do with node v8... will fix for v8 and back-test with v6. Wouldn't think there would be a difference between the two with simple object/array lookups but ok :)

[mitchellsimoens]

So the issue here, and it's an annoying one, was that [Object] was now going to print out to [Array]:

So I used A.print to get the same printed message. Don't like using values that aren't static strings but this was only way to get tests to pass on 6 and 8.

[dongryphon]

if this check is to prevent in from throwing... won't we have the same issue in the for loop below? Would this handle both?

    if (typeof obj !== 'object' || !(prop in obj)) {

[dongryphon]

Just realized we should probably check only here as well.. So that

    expect({ a: { b: 2}, c: true }).to.only.have.deep.property('a.b', 2);

Is reported as a failure.

Agree?