Merge branch 'release/0.5.17' into develop
Add init.js compilation
Remove comments and compile init.js and pixel.js
Optimize images

Use optimized PNGs instead of GIFs.
Javascript resources optimization

* inline small javascript
* load compiled resources
* use async loading
* load CSS before external javascripts
Bump version number to 0.5.18
Merge branch 'release/0.5.18'