Added instructions and small adaption for using on openSUSE

Hi,

I just added additional path for where to look for mkgmap since on openSUSE it's installed on some path not included so far.
Also I added some instructions for installing the needed packages on openSUSE installations.

Would be nice, if you could include this.

Cheers
Meinhard

P.S. This is my first pull request here on github.