chore(project): fix contributing/setup instructions
chore(project): fix contributing/setup instructions

`git clone` doesn't automatically set up a local tracking branch for
`master` because `develop` is the default branch now.
This will leave us checked out out in `develop`.
Doing a `git checkout master` will fix this.
But now `git flow init -d` doesn't leave us checked out in `develop` as
it dit before.
A `git checkout develop` will fix that, either before or after.
But doing it before `git flow init -d` will ensure that the user will
still end up shipshape even if `master` and not `develop` was the default
branch.

marviq/generator-bat,marviq/generator-bat,marviq/generator-bat