Added "removeLastSegment" methods.
Changed the way duration is calculated, this should fix some
durations that were sometimes incorrectly being calculated with tiny record segments.
Removed endSession: and "shouldTrackRecordSegments".
Removed "mergeRecordSegments:" and replaced it by "mergeRecordSegmentsUsingPreset:completionHandler:".
Fixed #74
Added check on CVPixelBufferPoolCreatePixelBuffer to avoid crashes when it fails.