Update README.markdown

Updating the install instructions as proposed in: https://github.com/robbyrussell/oh-my-zsh/issues/3516#issuecomment-76506726

README.markdown

@@ -25,11 +25,11 @@ Oh My Zsh is installed by running one of the following commands in your terminal
 
 #### via curl
 
-`curl -L https://raw.github.com/robbyrussell/oh-my-zsh/master/tools/install.sh | sh`
+`sh -c "$(curl -fsSL https://raw.github.com/robbyrussell/oh-my-zsh/master/tools/install.sh)"`
 
 #### via wget
 
-`wget https://raw.github.com/robbyrussell/oh-my-zsh/master/tools/install.sh -O - | sh`
+`sh -c "$(wget https://raw.github.com/robbyrussell/oh-my-zsh/master/tools/install.sh -O -)"`
 
 ## Using Oh My Zsh