init変更
getLayerNum
getLayersDataの実装

Signed-off-by: Naoya Kikuchi <ashidome@gmail.com>
Merge branch 'master' of https://github.com/ashidome/Paint-BuiLder---.git
Merge branch 'master' of https://github.com/ashidome/Paint-BuiLder---.git
Merge branch 'master' of https://github.com/ashidome/Paint-BuiLder---.git
Signed-off-by: Naoya Kikuchi <ashidome@gmail.com>