[myspace] Update extractor

fixed download and added support for downloading albums
Could you add a test (see the [youtube:playlist examples](https://github.com/rg3/youtube-dl/blob/42939b6129833e3fb9f4c22e4e9f4056df193af2/youtube_dl/extractor/youtube.py#L1036)).

Also, it's usually better to split different changes (in this case adding a new extractor) in different Pull Requests or at least different commits.