New version 0.1.0-alpha released !

What's new ?:
- added next few sounds
- start to implement simple 3D audio effects
- fixed audio volume changing
- fixed displaying map list
- fixed many memory leaks
- some fixes in HUD
- improved GUI
- possibility to take screenshots, show FPS's, stop/play music,
set to previous and next music track (see README.txt)
- update stb_image from SOIL library to 1.18 version