Read operations do not start at the start of the file

[sprague252]

When I pass an open IOStream to wavread or read_header, it generates an error if the file is not at the top. This is problematic if I have already done something with the file or if I have already called another of the WAV functions with the file. The workaround is to call seekstart(filehandle) before calling the WAV function. I suggest that you call seekstart at the beginning of the functions to avoid this issue.