Update README.md

Author: kminami

Diff for: README.md

@@ -4,6 +4,18 @@ Expand Include directive in API Blueprint
 This is a part of `aglio`.
 See https://github.com/danielgtaylor/aglio#including-files .
 
+# Install
+`npm install --save apib-include-directive`
+
+# Usage
+```javascript
+var apibIncludeDirective = require('apib-include-directive')
+
+var expanded = apibIncludeDirective.expand('/path/to/file.md')
+
+var expanded = apibIncludeDirective.includeDirective('/path/to', 'file content')
+```
+
 # License
 
 Copyright (c) 2016 Daniel G. Taylor