Update INSTALLATION.md instructions
Update INSTALLATION.md instructions

mienaikage/exercism-perl6,exercism/xperl6,mienaikage/xperl6,mienaikage/xperl6,mienaikage/exercism-perl6,exercism/xperl6,mienaikage/xperl6,mienaikage/exercism-perl6,exercism/xperl6