[pathmunge] fix duplicates in PATH variable for nginx and node plugins

plugins/available/nginx.plugin.bash

@@ -1,11 +1,8 @@
 cite about-plugin
 about-plugin 'manage your nginx service'
 
-# Set the path nginx
 export NGINX_PATH='/opt/nginx'
-
-# Add nginx to the path
-export PATH=$PATH:$NGINX_PATH/sbin
+pathmunge $NGINX_PATH/sbin after
 
 function nginx_reload() {
   about 'reload your nginx config'

plugins/available/node.plugin.bash

@@ -1,9 +1,7 @@
 cite about-plugin
 about-plugin 'Node.js helper functions'
 
-export PATH=./node_modules/.bin:$PATH
+pathmunge ./node_modules/.bin
 
 # Make sure the global npm prefix is on the path
-[[ `which npm` ]] && export PATH=$(npm config get prefix)/bin:$PATH
-
-
+[[ `which npm` ]] && pathmunge $(npm config get prefix)/bin