Update swig/python/README.txt

git-svn-id: https://svn.osgeo.org/gdal/trunk@27429 f0d54148-0727-0410-94bb-9a71ac55c965
Update HOWTO-RELEASE to update Python bindings to Pypi

git-svn-id: https://svn.osgeo.org/gdal/trunk@27430 f0d54148-0727-0410-94bb-9a71ac55c965
Merge branch 'trunk' into trunk_travis_macosx