Renamed `master?` to `fail_on_current_branch?` #34

Preparation for letting the user choose on which branches to fail
Wording: current_branch instead of branch #34
Config::Devtools knows about `fail_on_branch` #34

Defaults to the `master` branch
Fail on the configured branches #34
Make fail_on_branch master part of the default devtools.yml #34
Merge remote-tracking branch 'origin/master' into develry-rename

Conflicts:
	lib/develry/config.rb
	tasks/metrics/reek.rake