VirtualEnvWrapper lazy loading

virtualenvwrapper is good but it's initializing each time you open a new shell.

But it can delay its initialization: http://virtualenvwrapper.readthedocs.org/en/latest/install.html#lazy-loading

Here what's in my .zshrc:

export PROJECT_HOME=~/projects/
export WORKON_HOME=~/projects/ve
if [ -f "$(which virtualenvwrapper_lazy.sh)" ]; then
    source $(which virtualenvwrapper_lazy.sh)
fi