handleSkipBackward going back incorrect number of seconds

[pietrorea]

I've configured both skipForwardSeconds and skipBackwardSeconds like this:

player.skipForwardSeconds = 30
player.skipBackwardSeconds = 15

but I've noticed that handleSkipBackward goes back 30 seconds, not 15.

[pietrorea]

Opened PR https://github.com/tanhakabir/SwiftAudioPlayer/pull/179 to fix this