fix bug for MSYS users - makes several folders, fails on shell startup

* if $WORKON_HOME not defined, or folder missing, then when mkdir called must
* pass $WORKON_HOME in double-quotes "$WORKON_HOME" because there might be
* spaces that will be interpretted separately
* e.g. C:\Documents and Settings\.virtualenv makes 3 folders:
* "C:\Documents", "~/and" & "~/Settings/.virtualenv"

Author: bwanamarko

virtualenvwrapper.sh

@@ -118,7 +118,7 @@ function virtualenvwrapper_verify_workon_home {
         then
             echo "NOTE: Virtual environments directory $WORKON_HOME does not exist. Creating..." 1>&2
         fi
-        mkdir -p $WORKON_HOME
+        mkdir -p "$WORKON_HOME"
         RC=$?
     fi
     return $RC