Fix converter_jade_bss example

I don't have the Eigen3 on my local machine. 
So, before this patch I got:

/usr/lib/gcc/x86_64-linux-gnu/4.7/../../../x86_64-linux-gnu/crt1.o: In function '_start':
(.text+0x20): undefined reference to 'main'
collect2: error: ld returned 1 exit status
make[2]: *** [examples/undocumented/libshogun/converter_jade_bss] Error 1
make[1]: *** [examples/undocumented/libshogun/CMakeFiles/converter_jade_bss.dir/all] Error 2