add colored diff command

Brewfile

@@ -31,3 +31,4 @@ brew "tig"
 brew "realpath"
 brew "mackup"
 brew "lynx"
+brew "colordiff"

dot_zsh_aliases

@@ -23,6 +23,7 @@ alias hack='hacker'
 alias done='task_done'
 alias h='cd $HOME'
 alias sshpub='cat ~/.ssh/id_rsa.pub'
+alias diff='colordiff'
 
 # Show/hide hidden files in Finder
 alias show="defaults write com.apple.finder AppleShowAllFiles -bool true && killall Finder"