exclude most of doc directory from PiPy package

* this is because of a size limitation which we now exceed
  due ot our RTD docs and related images.
* includes doc/release/*.

MANIFEST.in

@@ -9,6 +9,6 @@ recursive-include apps *.*
 recursive-include python *.*
 recursive-include paraview *.*
 recursive-include test *.*
-recursive-include doc *.*
+recursive-include doc/release *.*
 global-exclude *.pdf
 global-exclude *.sw?