Fixes to 'Building and Installing' on the README
Fixes to 'Building and Installing' on the README

Fixed a typo and made a sentence clearer.

walls-of-doom/walls-of-doom,mafagafogigante/walls-of-doom,mafagafogigante/walls-of-doom,walls-of-doom/walls-of-doom,walls-of-doom/walls-of-doom,walls-of-doom/walls-of-doom,mafagafogigante/walls-of-doom