install.sh: use portable printf instead of echo

tools/install.sh

 set -e
 
+BLUE="\033[0;34m"
+GREEN="\033[0;32m"
+YELLOW="\033[0;33m"
+NOCOLOR="\033[0m"
+
 if [ ! -n "$ZSH" ]; then
   ZSH=~/.oh-my-zsh
 fi
 
 if [ -d "$ZSH" ]; then
-  echo "\033[0;33mYou already have Oh My Zsh installed.\033[0m You'll need to remove $ZSH if you want to install"
+  printf "${YELLOW}You already have Oh My Zsh installed.${NOCOLOR} You'll need to remove $ZSH if you want to install\n"
   exit
 fi
 
-echo "\033[0;34mCloning Oh My Zsh...\033[0m"
+printf "${BLUE}Cloning Oh My Zsh...${NOCOLOR}\n"
 hash git >/dev/null 2>&1 && env git clone --depth=1 https://github.com/robbyrussell/oh-my-zsh.git $ZSH || {
-  echo "git not installed"
+  printf "git not installed\n"
   exit
 }
 
-echo "\033[0;34mLooking for an existing zsh config...\033[0m"
+printf "${BLUE}Looking for an existing zsh config...${NOCOLOR}\n"
 if [ -f ~/.zshrc ] || [ -h ~/.zshrc ]; then
-  echo "\033[0;33mFound ~/.zshrc.\033[0m \033[0;32mBacking up to ~/.zshrc.pre-oh-my-zsh\033[0m";
+  printf "${YELLOW}Found ~/.zshrc.${NOCOLOR} ${GREEN}Backing up to ~/.zshrc.pre-oh-my-zsh${NOCOLOR}\n";
   mv ~/.zshrc ~/.zshrc.pre-oh-my-zsh;
 fi
 
-echo "\033[0;34mUsing the Oh My Zsh template file and adding it to ~/.zshrc\033[0m"
+printf "${BLUE}Using the Oh My Zsh template file and adding it to ~/.zshrc${NOCOLOR}\n"
 cp $ZSH/templates/zshrc.zsh-template ~/.zshrc
 sed -i -e "/^export ZSH=/ c\\
 export ZSH=$ZSH
 " ~/.zshrc
 
-echo "\033[0;34mCopying your current PATH and adding it to the end of ~/.zshrc for you.\033[0m"
+printf "${BLUE}Copying your current PATH and adding it to the end of ~/.zshrc for you.${NOCOLOR}\n"
 sed -i -e "/export PATH=/ c\\
 export PATH=\"$PATH\"
 " ~/.zshrc
 
 TEST_CURRENT_SHELL=$(expr "$SHELL" : '.*/\(.*\)')
 if [ "$TEST_CURRENT_SHELL" != "zsh" ]; then
-    echo "\033[0;34mTime to change your default shell to zsh!\033[0m"
+    printf "${BLUE}Time to change your default shell to zsh!${NOCOLOR}\n"
     chsh -s $(grep /zsh$ /etc/shells | tail -1)
 fi
 unset TEST_CURRENT_SHELL
 
-echo "\033[0;32m"'         __                                     __   '"\033[0m"
-echo "\033[0;32m"'  ____  / /_     ____ ___  __  __   ____  _____/ /_  '"\033[0m"
-echo "\033[0;32m"' / __ \/ __ \   / __ `__ \/ / / /  /_  / / ___/ __ \ '"\033[0m"
-echo "\033[0;32m"'/ /_/ / / / /  / / / / / / /_/ /    / /_(__  ) / / / '"\033[0m"
-echo "\033[0;32m"'\____/_/ /_/  /_/ /_/ /_/\__, /    /___/____/_/ /_/  '"\033[0m"
-echo "\033[0;32m"'                        /____/                       ....is now installed!'"\033[0m"
-echo "\n\n \033[0;32mPlease look over the ~/.zshrc file to select plugins, themes, and options.\033[0m"
-echo "\n\n \033[0;32mp.s. Follow us at http://twitter.com/ohmyzsh.\033[0m"
-echo "\n\n \033[0;32mp.p.s. Get stickers and t-shirts at http://shop.planetargon.com.\033[0m"
+printf "${GREEN}"
+echo '         __                                     __   '
+echo '  ____  / /_     ____ ___  __  __   ____  _____/ /_  '
+echo ' / __ \/ __ \   / __ `__ \/ / / /  /_  / / ___/ __ \ '
+echo '/ /_/ / / / /  / / / / / / /_/ /    / /_(__  ) / / / '
+echo '\____/_/ /_/  /_/ /_/ /_/\__, /    /___/____/_/ /_/  '
+echo '                        /____/                       ....is now installed!'
+echo ''
+echo ''
+echo 'Please look over the ~/.zshrc file to select plugins, themes, and options.'
+echo ''
+echo 'p.s. Follow us at http://twitter.com/ohmyzsh.'
+echo ''
+echo 'p.p.s. Get stickers and t-shirts at http://shop.planetargon.com.'
+echo ''
+printf "${NOCOLOR}"
 env zsh
-. ~/.zshrc