Add pyenv plugin

plugins/available/pyenv.plugin.bash

@@ -0,0 +1,14 @@
+cite about-plugin
+about-plugin 'load pyenv, if you are using it'
+
+export PYENV_ROOT="$HOME/.pyenv"
+export PATH="$PYENV_ROOT/bin:$PATH"
+[[ `which pyenv` ]] && eval "$(pyenv init -)"
+
+#Load pyenv virtualenv if the virtualenv plugin is installed.
+if pyenv virtualenv-init - &> /dev/null; then
+  eval "$(pyenv virtualenv-init -)"
+fi
+
+# Load the auto-completion script if pyenv was loaded.
+[[ -e $PYENV_ROOT/completions/pyenv.bash ]] && source $PYENV_ROOT/completions/pyenv.bash