added a note on shared eggs folder

--HG--
branch : distribute
extra : rebase_source : 09545a175010b1105b8223c90638e9180feeb1c2

README.txt

@@ -199,6 +199,10 @@ Install FAQ
   at `http://nightly.ziade.org/bootstrap.py`. The code is located at
   `http://bitbucket.org/tarek/buildout-distribute`.
 
+  Beware that if you use a shared eggs folder with buildout, you need to 
+  switch all buildouts that use it to distribute. This is due to the fact
+  that the setuptools eggs located in the shared folder will be replaced
+  by a fake one, alongside distribute.
 
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