Add message in gitbook command line

bin/gitbook.js

@@ -0,0 +1,7 @@
+#! /usr/bin/env node
+
+var color = require('bash-color');
+
+console.log(color.red("You need to install 'gitbook-cli' to have access to the gitbook command anywhere on your system."));
+console.log(color.red("If you've installe this package globally, you need to uninstall it."));
+console.log(color.red(">> Run 'npm uninstall -g gitbook' then 'npm install -g gitbook-cli'"));

package.json

@@ -48,6 +48,9 @@
         "type": "git",
         "url": "https://github.com/GitbookIO/gitbook.git"
     },
+    "bin": {
+        "gitbook": "./bin/gitbook.js"
+    },
     "keywords": [
         "git",
         "book",