100 LEDs

Hmm, I missed that. It looks like it was meant to be driven by 10-15 volts, so that would make sense. You could always tie the signal into an NPN transistor to source power (similar to a Darlington Pair), but you’d need one for each LED. I only paid $2 for a pack of 100 BC546’s, which can give 100mA, but that does increase the total cost and complexity by a fair amount. I guess the CD4017BE may not be the best IC for this, but I still think that a microprocessor would be overkill and too costly for this.
Edit: updated schematic

"a microprocessor would be overkill and too costly for this." Well, a '328P is just $2.50 http://www.mouser.com/ProductDetail/Atmel/ATMEGA328P-PU/?qs=K8BHR703ZXhdUS2n3IW%2fRITwfrPGjO%2fc If the internal oscillator is used, then only a 10K pullup and the current limit resistors are needed.