modified install script to output a safe PATH-update (fixes #735)

scripts/installer/installer

@@ -89,7 +89,7 @@ function install_abra_release {
   if [ $? -ne 0 ]; then
       echo "$(tput setaf 3)WARNING: $HOME/.local/bin/ is not in \$PATH! If you want to run abra by just typing "abra" you should add it to your \$PATH! To do that run this once and restart your terminal:$(tput sgr0)"
       p=$HOME/.local/bin
-      com="echo PATH=\$PATH:$p"
+      com='echo PATH="$PATH:'"$p"'"'
       if [[ $SHELL =~ "bash" ]]; then
           echo "$com >> $HOME/.bashrc"
       elif [[ $SHELL =~ "fizsh" ]]; then