Added another path for virtualenvwrapper plugin

When you install python via brew on OSX, pip is installed into /usr/local/share/python/ and all packages installed with this pip are installed here.

plugins/virtualenvwrapper/virtualenvwrapper.plugin.zsh

 WRAPPER_FOUND=0
-for wrapsource in "/usr/bin/virtualenvwrapper.sh" "/usr/local/bin/virtualenvwrapper.sh" "/etc/bash_completion.d/virtualenvwrapper" ; do
+for wrapsource in "/usr/bin/virtualenvwrapper.sh" "/usr/local/bin/virtualenvwrapper.sh" "/usr/local/share/python/virtualenvwrapper.sh" "/etc/bash_completion.d/virtualenvwrapper" ; do
   if [[ -e $wrapsource ]] ; then
     WRAPPER_FOUND=1
     source $wrapsource