refactoring TimeHelper-method => 5.minutes.from_now
refactoring TimeHelper-method => days.from_now
refactoring in step_def: TimeHelper => minutes.from_now and days.from_now
refactoring in model-specs: TimeHelper => minutes/days.from_now
TimeHelper: removed surplus methods
step def: TimeHelper => minutes.from_now
refactoring GuessSpec: TimeHelper => be_within
refactoring step def: TimeHelper => be_within
removed surplus module TimeHelper from lib