Allow Bandcamp to parse and download all albums

[MasterFocus]

Hello,

First of all, thanks in advance for this great tool. 😄
I'm really happy with all the work you and others have put into this and I hope my commits may be helpful.

Before going any further, it is worth mentioning how some special Bandcamp pages seem to work:

....bandcamp.com/releases    ==>    mirrors the page of the artist's latest album
....bandcamp.com/music       ==>    shows a grid with all albums of the band
....bandcamp.com/merch       ==>    shows a bunch of merchandise

The main URL (....bandcamp.com) usually mirrors one of those.

Here's an example where /releases is mirrored: https://mothermooch.bandcamp.com/
Here's an example where /music is mirrored: https://mississippibones.bandcamp.com/
_{(examples checked as of 2015/October/31 - may differ in the future)
(I can't find any examples right now, but I'm 100% sure some bands choose to mirror /merch)}

While testing SoundScraper, I couldn't download all albums from a certain band.
This band's main URL was mirroring /music, so it couldn't be parsed correctly.
SoundScraper would also fail for any artists mirroring /merch, for obvious reasons.

So, these are my main proposed additions with this Pull Request:
[1] The /music page is now accessed when only the artist's username is provided
[2] The /music page is now parsed, recursively calling the relevant method for each album URL

This only introduces a small bug: the limit of tracks is applied for each album separately.
It's like "num_tracks" actually means "num_tracks_per_album".
_{(if num_tracks=2 and the band has 5 albums, you're going to download 10 tracks)}
I'm sure it's an easy fix, but I didn't have time to give it a closer look. 😐

I'm kinda busy and had to use the browser editor to commit my changes, so I may have messed up the indentation. Sorry. 😑

Best regards,

Antonio

[Miserlou]

Hey MasterFocus!

Thanks for the PR! I'm happy to accept this update, although it seems like you have introduced some formatting errors which cause the tests to fail.

Can you please run your changes through PEP8ify and make sure that the tests pass? It'd also be great if you could write a test for the specific case you are adding support for.

Thanks!

[MasterFocus]

This is indeed my first PR ever on GitHub, so I just noticed the indentation problem. I'll try to fix that ASAP. I'll also try to add tests as you mentioned in the near future. Once again, thanks for your work (and your patience 😅)!

[Miserlou]

Merged, and published as version 0.20.0

Thank you for your contribution! :D

[Miserlou]

This has already been useful for me today!! Thanks!