Added support for sprint disable

	* Configured init to support enable or disable of sprint
	* Added validation to bugfix, feature, and all other helpers
NEEDS FIX

	* Removed check for sprint prefix
	* Removed check for pull request support
	* Need fix when validating if init should run
	* Need fix when requiring git flow init
Fixed init on sprint
Added version tag to init
Merge branch 'feature/sprint' of github.com:meligaletiko/gitflow into feature/sprint