Merge pull request #83 from Kiryuanzu/add_homebrew_install_doc

add other install description

Author: ko1

EN/2_mri_structure.md

@@ -35,6 +35,7 @@ If you use `apt-get` (or `apt`) for package management in your environment, then
 $ sudo apt-get install git ruby autoconf bison gcc make zlib1g-dev libffi-dev libreadline-dev libgdbm-dev libssl-dev libyaml-dev
 ```
 
+If you would like to install other than `apt-get`, see for example [Home · rbenv/ruby\-build Wiki](https://github.com/rbenv/ruby-build/wiki)
 ## Exercise: Clone the MRI source code
 
 Use the following commands:

JA/2_mri_structure.md

@@ -33,6 +33,8 @@ git、ruby、autoconf、bison、gcc (or clang, etc）、make が必須です。
 $ sudo apt-get install git ruby autoconf bison gcc make zlib1g-dev libffi-dev libreadline-dev libgdbm-dev libssl-dev libyaml-dev
 ```
 
+`apt-get` 以外でインストールしたい場合は、例えば [Home · rbenv/ruby\-build Wiki](https://github.com/rbenv/ruby-build/wiki) を参照してみてください。
+
 ## 演習: MRI のソースコードを clone
 
 1. `$ mkdir workdir`