Allow gitflow.feature.finish.no-ff to be configured during gt flow init.

[mahlon-gumbs]

• defaults to true

This is in response to https://github.com/petervanderdoes/gitflow-avh/issues/291 which has bitten me in the past as well.

[jkankiewicz]

The Incorporating a finished feature on develop section of A successful Git branching model doesn't make an exception for a feature branch with only one commit on so it would be nice if git flow init prompted the user with the option to make git flow feature finish <name> work consistently for all feature branches without having to remember to also invoke git config gitflow.feature.finish.no-ff true afterwards (#140).

[ChrisJStone]

I'm in the process of updating gitflow. If you could kindly resubmit your pull request against my fork here as it appears this fork is no longer being updated.