Method to determine the size of a JS object literal (associative array, as some call it)

[mtheoryx]

Implement this method from SO: http://stackoverflow.com/a/6700/4038230

Remember, the project doesn't want adding things to Object.prototype, and this copypasta answer doesn't, but try to not alter Object either.

[mtheoryx]

I'll take this, as mentioned in #23