Add floor and ceiling

[SharkBeard]

Add floor and ceiling methods to TimeOfDay. This is useful for scheduling things at specific time intervals after doing arithmetic. For example to only schedule things in 15-minute increments.

[jackc]

Did you maybe forget to commit something? A test is failing:

  1) Error:
TimeOfDay::round_nearest#test_0001_rounds to the given nearest number of seconds:
NameError: undefined local variable or method `round_sec' for #<Tod::TimeOfDay:0x00007fe0c29ab5c8>
Did you mean?  round
    /Users/jack/dev/tod/lib/tod/time_of_day.rb:75:in `floor'
    /Users/jack/dev/tod/lib/tod/time_of_day.rb:85:in `round'
    /Users/jack/dev/tod/test/tod/time_of_day_test.rb:129:in `block (3 levels) in <top (required)>'