Changed clock prescalers and number of samples taken, bug fixes

decreased number of samples per bit about 5 times, thus decreasing
overhead by spending less time in the interrupt routine and increasing
accuracy because we have 5 times less chance to pickup a corrupted
sample by random noise yet enough samples to compensate for clock drifting,
fixed RX for ATMega @8MHz

RX Tested to work on ATTiny85 1Mhz and 8Mhz, ATMega328 8Mhz and 16Mhz, believed to work on others