Fix to "flac to wav" conversion

[AMairesse]

Hi,

Thanks for your great project, I have been working a little on it those past days and I will send you some pull request if that's ok for you. For easier review I decided to go with small pull requests so I have 2 or 3 others which should follow this one. Feel free to review my fork and take all if you prefer.

Anyway this pull request is about the conversion from flac to wav, there was an issue if there was mixed files inside directories :

• if the last file was a wav file the flac files from the directories wouldn't be converted and it would fail when we need to read them because the extension was already changed in the list
• if the last file was a flac file it would failed when trying to convert the first wav file

I've also some PEP8 fixes coming with, nothing really important but it make a lot of "noise" in this first pull request... Sorry.

Thanks, Antoine.

[domerin0]

Hey, thanks for your pr, it really cleans it up. I was worried there could be an issue with the conversion, I'm glad you clarified that (and offered a fix!).