Update OALAudioTrack.m

Changed because it caused a crash in Apportable. Worked fine under iOS.

Explanation:
Apple's docs say that we can access 'error' parameter only if the value returned by [AVAudioPlayer initWithContentsOfURL:error:] is nil.
Update OALAudioTrack.m
Merge pull request #63 from jacopious/patch-1

Update OALAudioTrack.m
Fixed ALSource setBuffer: crash when previous buffer gets deallocated.
Merge pull request #67 from alunbestor/master

Fixed crash in ALSource setBuffer: if previous buffer gets deallocated
Workaround for issue 65: Audio does not resume after it has been suspended by iOS (iPhone 5s & iOS 7.1)
https://github.com/kstenerud/ObjectAL-for-iPhone/issues/65
Update to fix new warnings.
Merge pull request #68 from mysugr/feature/issue-65

Workaround for issue 65: Audio does not resume after it has been suspend...
Update podspec to upcoming 2.4 release.
Podspec: Handle new lint requirement.
Merge branch 'master' of github.com:kstenerud/ObjectAL-for-iPhone