Change comment about AVAssetExportPresetPassthrough with Instagram 4.2.7
Some refactoring with Statement Expressions
Add checking AVAsset.compatibleWithSavedPhotosAlbum before write to SavedPhotosAlbum
Add checking naturalSize for determine the limit of maximum frame rate
Continue exporting while application enter background
Fix UI was not updated on finish of exporting while application was background

Change `-updateUI` runs in main queue
Merge branch 'develop'

* develop:
  Fix UI was not updated on finish of exporting while application was background
  Continue exporting while application enter background
  Add checking naturalSize for determine the limit of maximum frame rate
  Add checking AVAsset.compatibleWithSavedPhotosAlbum before write to SavedPhotosAlbum
  Some refactoring with Statement Expressions
  Change comment about AVAssetExportPresetPassthrough with Instagram 4.2.7