Added type hinting for array type arguments

[marianoasselborn]

Hi, thanks for your work man, it's awesome!

As these methods do not accept $attributes in any other type than an array, I put some type hints on them :)

[Omranic]

Thanks @marianoasselborn for your contribution, that's really appreciated.
But please note that develop branch is currently under heavy development which has been re-written from scratch & things has changed a lot, so next release won't be 1.x, instead it will be 2.x, which don't have these methods anyway. Please check the develop branch & feel free to send any fixes or PRs there, thanks again 👍