Revert "Introduce "copy" METHOD for installation"

This reverts commit 6acce5246a.

install.sh

@@ -109,18 +109,6 @@ nvm_do_install() {
       exit 1
     fi
     install_nvm_as_script
-  elif [ "~$METHOD" = "~copy" ]; then
-    local COPY=true
-    if [ $DIR = $NVM_DIR ]; then
-      echo "=> install.sh is already in $NVM_DIR"
-      COPY=false
-    elif [ -d $NVM_DIR ]; then
-      echo "=> $NVM_DIR already exists and its contents will be replaced"
-    fi
-    mkdir -p $NVM_DIR
-    if $COPY; then
-      cp -R $DIR/* $NVM_DIR
-    fi
   fi
 
   echo