st: Update to 0.4.1 and add support for custom config

Simple terminal, doesn't have support for runtime configs(which is good, because it makes it super fast), but config is set in compile time, with header file. This commit adds support for setting custom config(for example to change theme).

I also updated it, because it now supports fontconfig, so you don't have to patch your fonts anymore like you do in uxrvt and similar ;)