Revert "Reverted changed behaviour of deviation_of"

This reverts commit 21b6d4c1bb79b184f3d0d24dc3f2e7aa43fc7bed.
Implemented first versions of before? and after?
Adding Guardfile
Implemented after?
Increased version
Renamed deviation_of to time_between
Merge pull request #9 from injixo/deviation-of-refactoring

deviation_of refactoring