v1.2.0-v1.2.1

Changes

• Add a source-map to published npm package
• Fixes a INVALID_ENUM issue, see #4
• Fix bugs caused by VAO in pixi.js 4.2.1 and above, now you can use Live2D in pixi.js 4.0.3~4.3.2 (the latest version now)
• Refactoring MatrixStack using glMatrix-mat4, thank @ivanpopelyshev for suggestion! (see #3)
• seperate pixi.js from pixi-live2d bundle.