bump up the version to 0.9

I want to use 1.0rc1, but cabal doesn't like this format.
I read that 1.1.5.9.2 was the version number for the 2nd release
candidate of Cabal 1.1.6, so it makes sense to use 0.9 (or 0.9.1?) for
the first release candidate of Hawk 1.0