The first century spans from the year 1 up to and including the year 100, the second century - from the year 101 up to and including the year 200, etc.
Given a year, return the century it is in.
1705 --> 18
1900 --> 19
1601 --> 17
2000 --> 20
2742 --> 28
Note: this kata uses strict construction as shown in the description and the examples, you can read more about it here
def century(year)
(year/100.0).ceil
end