* Doesn't search song on Spotify if '--no-metadata' passed
* Doesn't search song on Spotify if '--no-metadata' passed
* Doesn't war user that 'no metadata found' if '--no-metadata' passed
* Fixes#272 by refactoring global log to conventional global as used by logzero
* Remove unnecessary logger from download_single, which was a test case
* Remove unnecessary logger from main(), which was a test case