Add new ring buffer constructer fn: bools: 

* Allows you to write a list of true and false
  more flexibly:

  (bools 1, 0, 1, 1) #=> [true, false, true, true]

* Returns a RingArray

* Handles nils, false and treats non-nil, non-false
  and non-0 values as truthy:

  (bools :a, 1, 0, false, nil) #=> [true, true, false, false, false]
Fix TB303 regression introduced in 2.1:

* Now sounds as it did in 2.0 but with the extra controls :-)