Add nvm_strip_iojs_prefix

nvm.sh

@@ -358,6 +358,16 @@ nvm_is_iojs_version() {
   [ "_$(echo "$1" | cut -c1-5)" = "_iojs-" ]
 }
 
+nvm_strip_iojs_prefix() {
+  local NVM_IOJS_PREFIX
+  NVM_IOJS_PREFIX="$(nvm_iojs_prefix)"
+  if [ "_$1" = "_$NVM_IOJS_PREFIX" ]; then
+    echo
+  else
+    echo "$1" | command sed "s/^$NVM_IOJS_PREFIX-//"
+  fi
+}
+
 nvm_ls() {
   local PATTERN
   PATTERN="$1"
@@ -1202,6 +1212,7 @@ nvm() {
     "unload" )
       unset -f nvm nvm_print_versions nvm_checksum \
         nvm_iojs_prefix nvm_node_prefix \
+        nvm_strip_iojs_prefix \
         nvm_is_iojs_version \
         nvm_ls_remote nvm_ls nvm_remote_version \
         nvm_version nvm_rc_version \