Revert ".zshrc: Use simpler pyenv initialization"

This reverts commit 54b1eaaa88.

When I go back to Linux I realize how annoying this is. Let's just
use the git checkout version on all systems.

.zshrc

@@ -68,8 +68,19 @@ export ANSIBLE_HOSTS=hosts
 # Enable node version manager (nvm)
 [[ -s ~/.nvm/nvm.sh ]] && . ~/.nvm/nvm.sh
 
-# Initialize pyenv if it exists
-if which pyenv > /dev/null; then eval "$(pyenv init -)"; fi
+# Enable pyenv
+# See: https://github.com/yyuu/pyenv#basic-github-checkout
+if [[ -d ~/.pyenv ]]; then
+    export PYENV_ROOT="$HOME/.pyenv"
+    PATH="$PYENV_ROOT/bin:$PATH"
+
+    eval "$(pyenv init -)"
+    # optionally enable pyenv-virtualenv
+    # See: https://github.com/yyuu/pyenv-virtualenv
+    if [[ -d ~/.pyenv/plugins/pyenv-virtualenv ]]; then
+        eval "$(pyenv virtualenv-init -)"
+    fi
+fi
 
 # Initialize jenv if it exists
 if which jenv > /dev/null; then