fix #1 typo / misspelling of PREFIX

PREFIX not PREFIIX as per #1

README.md

@@ -83,7 +83,7 @@ echo "Latest node.js $BASE_VER is $NODEJS_VER"
 
 Just set BOTH `NODE_PATH` and `NPM_CONFIG_PREFIX`.
 The install path will be the preceding `lib/node_modules`
-(which you usually want to be the same as `NPM_CONFIG_PREFIIX` anyway).
+(which you usually want to be the same as `NPM_CONFIG_PREFIX` anyway).
 
 ```bash
 export NPM_CONFIG_PREFIX=/tmp/user/local