Fixed segfault caused by FD_ISSET() on negative fd

Reported by Kris Siwiec
Updated source tarball URLs in README.md
Updated .gitignore
Fixed non-ASCII characters in window bar, issue #88
Updated source tarball URLs in README.md
Use bgcol as window background pixel; fixed issue #89
Fixed build for giflib version >= 5.0; fixed issue #90
Save image list to a file
Local config + TODO