This also requires switching from `rustc-serialize` to `serde`
for the arguments handling, so the dependency on `rustc-serialize`
has been removed and a dependency on `serde` has been added.
Due to https://github.com/rust-lang/rust/issues/18810 (https://github.com/rust-lang/rfcs/issues/752)
it is not possible to have an inner attribute in a file that gets
used with `include!`.
Specifying the attribute on each parser module is less precise and more
duplication but it will at least work for that case. If a user wants to
apply the rustfmt on the whole module they can still add an outer
attribute manually as well.
