Changed the name of nice timer to nicetimer_238

Preparing to make changes to the nice timer functions to allow for cross
  chip compatability between the Arduino Duemilinova, Uno, Leonardo, and Mega
added nicetimer library support for ATmega32U4

nicetimer.h now loads individual chip timer libraries
niceTimer_32U4 has functions for timers 0, 1, and 3 but not 4
niceTimer_2560 has no functions