Don't hardcode the initial syllable

Hi Brandon! I've really enjoyed *Cycles Per Instruction* and playing with this program. 

When I first invoked `./MumbleyMumbler.pl ./Model` as specified in the README, the script spewed errors because it hardcoded an initial value of `$syl` that wasn't in `./Model`; this caused `getRandomFollower` to fail because `$model{$k}` would be null.

This patch modifies the script to pick a random initial syllable from the model so we're guaranteed to have a following syllable. Thanks for taking a look — I'm really excited to play with this in my own music projects.