Racketのインストールに失敗する

## TL;DR
homebrewで `minimal-racket`がインストール済みだと `racket` のインストールに失敗する。

## 現象
```
% brew install --cask racket
==> Downloading https://mirror.racket-lang.org/installers/8.1/racket-8.1-x86_64-macosx-cs.dmg
Already downloaded: /Users/kuranari/Library/Caches/Homebrew/downloads/8ab3018728b67448918787702e5bce6c29080b78e9cd283d30b3541a127f6cc2--racket-8.1-x86_64-macosx-cs.dmg
==> Installing Cask racket
==> Moving App Suite 'Racket v8.1' to '/Applications/Racket v8.1'
==> Linking Binary 'drracket' to '/usr/local/bin/drracket'
==> Linking Binary 'gracket' to '/usr/local/bin/gracket'
==> Linking Binary 'gracket-text' to '/usr/local/bin/gracket-text'
==> Linking Binary 'mred' to '/usr/local/bin/mred'
==> Linking Binary 'mred-text' to '/usr/local/bin/mred-text'
==> Linking Binary 'mzc' to '/usr/local/bin/mzc'
==> Linking Binary 'mzpp' to '/usr/local/bin/mzpp'
==> Linking Binary 'mzscheme' to '/usr/local/bin/mzscheme'
==> Linking Binary 'mztext' to '/usr/local/bin/mztext'
==> Linking Binary 'pdf-slatex' to '/usr/local/bin/pdf-slatex'
==> Linking Binary 'plt-games' to '/usr/local/bin/plt-games'
==> Linking Binary 'plt-help' to '/usr/local/bin/plt-help'
==> Linking Binary 'plt-r5rs' to '/usr/local/bin/plt-r5rs'
==> Linking Binary 'plt-r6rs' to '/usr/local/bin/plt-r6rs'
==> Linking Binary 'plt-web-server' to '/usr/local/bin/plt-web-server'
==> Unlinking Binary '/usr/local/bin/plt-web-server'
==> Unlinking Binary '/usr/local/bin/plt-r6rs'
==> Unlinking Binary '/usr/local/bin/plt-r5rs'
==> Unlinking Binary '/usr/local/bin/plt-help'
==> Unlinking Binary '/usr/local/bin/plt-games'
==> Unlinking Binary '/usr/local/bin/pdf-slatex'
==> Unlinking Binary '/usr/local/bin/mztext'
==> Unlinking Binary '/usr/local/bin/mzscheme'
==> Unlinking Binary '/usr/local/bin/mzpp'
==> Unlinking Binary '/usr/local/bin/mzc'
==> Unlinking Binary '/usr/local/bin/mred-text'
==> Unlinking Binary '/usr/local/bin/mred'
==> Unlinking Binary '/usr/local/bin/gracket-text'
==> Unlinking Binary '/usr/local/bin/gracket'
==> Unlinking Binary '/usr/local/bin/drracket'
==> Backing App Suite 'Racket v8.1' up to '/usr/local/Caskroom/racket/8.1/Racket v8.1'
==> Removing App Suite '/Applications/Racket v8.1'
==> Purging files for version 8.1 of Cask racket
Error: It seems there is already a Binary at '/usr/local/bin/raco'.
```

## 原因
minimal-racketがインストール済みだったこと

## 対応
minimal-racketをuninstall

```
% brew uninstall minimal-racket
Uninstalling /usr/local/Cellar/minimal-racket/8.1... (1,950 files, 113.9MB)
```

## 結果
```
% brew install --cask racket
==> Downloading https://mirror.racket-lang.org/installers/8.1/racket-8.1-x86_64-macosx-cs.dmg
Already downloaded: /Users/kuranari/Library/Caches/Homebrew/downloads/8ab3018728b67448918787702e5bce6c29080b78e9cd283d30b3541a127f6cc2--racket-8.1-x86_64-macosx-cs.dmg
==> Installing Cask racket
==> Moving App Suite 'Racket v8.1' to '/Applications/Racket v8.1'
==> Linking Binary 'drracket' to '/usr/local/bin/drracket'
==> Linking Binary 'gracket' to '/usr/local/bin/gracket'
==> Linking Binary 'gracket-text' to '/usr/local/bin/gracket-text'
==> Linking Binary 'mred' to '/usr/local/bin/mred'
==> Linking Binary 'mred-text' to '/usr/local/bin/mred-text'
==> Linking Binary 'mzc' to '/usr/local/bin/mzc'
==> Linking Binary 'mzpp' to '/usr/local/bin/mzpp'
==> Linking Binary 'mzscheme' to '/usr/local/bin/mzscheme'
==> Linking Binary 'mztext' to '/usr/local/bin/mztext'
==> Linking Binary 'pdf-slatex' to '/usr/local/bin/pdf-slatex'
==> Linking Binary 'plt-games' to '/usr/local/bin/plt-games'
==> Linking Binary 'plt-help' to '/usr/local/bin/plt-help'
==> Linking Binary 'plt-r5rs' to '/usr/local/bin/plt-r5rs'
==> Linking Binary 'plt-r6rs' to '/usr/local/bin/plt-r6rs'
==> Linking Binary 'plt-web-server' to '/usr/local/bin/plt-web-server'
==> Linking Binary 'raco' to '/usr/local/bin/raco'
==> Linking Binary 'scribble' to '/usr/local/bin/scribble'
==> Linking Binary 'setup-plt' to '/usr/local/bin/setup-plt'
==> Linking Binary 'slatex' to '/usr/local/bin/slatex'
==> Linking Binary 'slideshow' to '/usr/local/bin/slideshow'
==> Linking Binary 'swindle' to '/usr/local/bin/swindle'
==> Linking Binary 'racket' to '/usr/local/bin/racket'
==> Linking Manpage 'drracket.1' to '/usr/local/share/man/man1/drracket.1'
==> Linking Manpage 'gracket.1' to '/usr/local/share/man/man1/gracket.1'
==> Linking Manpage 'mred.1' to '/usr/local/share/man/man1/mred.1'
==> Linking Manpage 'mzc.1' to '/usr/local/share/man/man1/mzc.1'
==> Linking Manpage 'mzscheme.1' to '/usr/local/share/man/man1/mzscheme.1'
==> Linking Manpage 'plt-help.1' to '/usr/local/share/man/man1/plt-help.1'
==> Linking Manpage 'racket.1' to '/usr/local/share/man/man1/racket.1'
==> Linking Manpage 'raco.1' to '/usr/local/share/man/man1/raco.1'
==> Linking Manpage 'setup-plt.1' to '/usr/local/share/man/man1/setup-plt.1'
🍺  racket was successfully installed!
```