class Chronic::Span

ending times of the span (they will be of class Time)
Range, you can use #begin and #end to get the beginning and
A Span represents a range of time. Since this class extends

def +(seconds)

resulting Span
Add a number of seconds to this span, returning the 
def +(seconds)
  Span.new(self.begin + seconds, self.end + seconds)
end

def -(seconds)

resulting Span
Subtract a number of seconds to this span, returning the 
def -(seconds)
  self + -seconds
end

def to_s

Prints this span in a nice fashion 
def to_s
  '(' << self.begin.to_s << '..' << self.end.to_s << ')'
end

def width

Returns the width of this span in seconds 
def width
  (self.end - self.begin).to_i
end