corrected getStream() declaration for SharedPythonOStream
corrected getStream() declaration for SharedPythonOStream

In my previous commit, I removed the const keyword from the definition but left it
in the declaration. This is a good time to not that I'm taking the const keyword
out because the compiler errors when it tries to cast the stringstream into
a const ostream.

breznak/nupic,breznak/nupic,breznak/nupic