[Mac] macOS Sierra にHomebrewをインストール

macOS Sierra では，特にエラーも生じず，ターミナルにスクリプトを貼り付けて実行するだけでインストール可能です．(24. Sep. 2017)

事前に，Xcodeとcommand line toolsをダウンロードしておきます．
その後に，Homebrewのインストールをおこないます．
インストールは，ターミナルに以下のスクリプトを貼り付けて，実行するだけです．

$ /usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

/usr/local の権限が書き換えられているという問題が報告されているようですが，以下のようにトラブルシューティングしても特に問題はなさそう．

$ brew doctor

Your system is ready to brew.

とりあえず，様子を見てみることにします．

噂によると，brew doctor を実行すると，以下のようなメッセージが出るとのことなのですが…．
Please note that these warnings are just used to help the Homebrew maintainers with debugging if you file an issue. If everything you use Homebrew for is working fine: please don't worry and just ignore them. Thanks!

Warning: /usr/local is not writable. 
You should probably change the ownership and permissions of /usr/local back to your user account.

 sudo chown -R $(whoami) /usr/local

Warning: /usr/local is not writable. 
Even if this directory was writable when you installed Homebrew, other software may change permissions on this directory. For example, upgrading to OS X El Capitan has been known to do this. Some versions of the "InstantOn" component of Airfoil or running Cocktail cleanup/optimizations are known to do this as well.

You should probably change the ownership and permissions of /usr/local back to your user account.

 sudo chown -R $(whoami) /usr/local

Warning: You are using OS X 10.12. 
We do not provide support for this pre-release version. You may encounter build failures or other breakages. Warning: Your Homebrew is outdated. You haven't updated for at least 24 hours. This is a long time in brewland! To update Homebrew, run `brew update`.