1.5.4

Changelog:

saddy

• Added a settings for generating texture atlas in ShoeBox (#21)
• Instances in sad::animations::Group could be played now sequentially (#30)

atlasgen

• Better atlas packing algorithm is integrated, support for replaced algorithms (#3 and #31 )
• Fixed issues #47 and #48
• Now user could duplicate texture in packer, via "--non-unique-textures" option (#49)
• Implemented merging multiple atlases into one (#49)