add a bits_per_sample check when reading WAVE_FORMAT_IEEE_FLOAT
add a bits_per_sample check when reading WAVE_FORMAT_IEEE_FLOAT

Currently hound only supports reading 32-bit floating point samples. It
is possible that we might want to support 64-bit floating point samples
in the future, however we will wait until somebody encouters a 64-bit
float wav file in the wild.

ruuda/hound,ruud-v-a/hound