README.md in imap_mogura-0.2.0 vs README.md in imap_mogura-0.2.1.pre.dev

@@ -5,11 +5,13 @@
 ## Installation
 
 To install this gem, just run as following. You can get the gem from [RubyGems.org](https://rubygems.org/).
 
 ```console
-$ gem install imap_mogura
+$ gem install imap_mogura --pre
 ```
+
+(This branch is `develop`, that means this is a pre-release version. You can install this version by specifying `--pre` option.)
 
 ## Usage
 
 Create `rules.yml` and write rules like following.