[WIP] prepare release 1.0.0

fix #91

this actually is ready but should only be merged right before release.
I would use ``~1.0`` (which is equivalent to ``1.*``). It advocates the best practice of using the ``~`` operator ofr libraries following semver, and it makes things easier when bumping the requirement (if you ask a contributor to bump the requirement to 1.1 in a PR using a new feature, he will probably change the constraint to ``1.1.*`` if he does not know composer well, when using this ``1.*`` range)