[Reverb]

- num diffusion steps is template param
- Contructor: use initializer list for delays per diffusion step
- added param for feedback delay min and max

tests/test_mix.cpp

@@ -136,7 +136,7 @@ void test_reverb()
 	std::cout << "----------------------------------------------" << std::endl;
 	std::cout << "test_reverb()" << std::endl;
 
-	Reverb<double, 8> rev(32);
+	Reverb<double, 8, 3> rev({32}, 1, 2);
 
 	float data_in[10] = {1, 2, 3, 4, 5, 6, 7,8, 9, 10};
 	float data_out[10] = {0, 0, 0, 0, 0, 0, 0,0, 0, 0};