v1.3.2 alpha

Merge branch 'dev' at v1.3.2-alpha.
Update packages.

Fixed:

• Won't reject an entire song if it has no album art.
• Removed flawed concurrencyLimiter code, reintroduced async.js for that.

Other:

• Updated to use fluent-ffmpeg 2.0.0-rc2.
• Refactored auth and dev-auth modules.