Fixed Soundcloud stream_url fetching (#42)

stream_url and stream_url location are saved when song is inserted to
database. Then, on each suggestion, the stream_url location is checked
if it’s valid; if not, a new, valid stream_url location will be fetched
using the existing stream_url.
Aliased soundcloud_last_working_stream_url (#42)

Aliased soundcloud_last_working_stream_url to soundcloud_url for
compatibility.
Merge branch 'develop'