Lazy-functions is only provided, when speaklater presented in system.

Hi there,

I've moved `speaklater` from required packages to optional ones. So you can use flask-babel without using extra one package. Why? As a next step I want add basic debianization, 'cause I actually want install your module as a Debian package.

PS As a bonus I added `build_sphinx` and `test` to available `setup.py` options.