Add another param to `get`

[ardok]

What do you think of adding a default value param into get?

(dotty.get(obj, 'a.b.c') || []).length

// instead, we could do this

dotty.get(obj, 'a.b.c', []).length

// hence, interface would look like

var get = module.exports.get = function get(object, path, defaultVal) {
...

[stramel]

Duplicate of #7