file_size option to display bytes as int when size < 1000

[zwimer]

Right now file_size(10) spits back 10.0 Bytes by default. Users can adjust formatting, however, there is no option to differentiate between when the number of bytes is small enough that the Byte or Bytes suffix is used. An option for this should be added.

With this option enabled (ideally by default):
Ex:
file_size(1) could print 1 Byte
file_size(10) could print 10 Bytes
file_size(1000) could print 1.0 kB

[zwimer]

This makes logical sense since you cannot have a decimal number of bytes in a file (which the function currently accepts given that value is defined as an int).