tm1640.h header must be installed before the binaries can be successfully compiled

When building the library on a clean machine the tm1640.h cannot be found:

> scons: Reading SConscript files ...
> scons: done reading SConscript files.
> scons: Building targets ...
> gcc -o src/main.o -c src/main.c
> src/main.c:17:20: fatal error: tm1640.h: No such file or directory