Fix my busted 1512c0e2a64e patch to libbe/util/encoding.py.

Fix my busted 1512c0e2a64e patch to libbe/util/encoding.py.

Some temporary changes to encoding.py seem to have been added to
  commit 1512c0e2a64e19c8d4e5697257a4df5ddd8bc727
  Author: W. Trevor King <wking@drexel.edu>
  Date:   Tue Nov 8 07:14:43 2011 -0500
by accident.

The initial change came from discussions with Niall Douglas, during
which I realized that "filesystem encoding" ususally means the
encoding for the *path*, not the *contents*.  To avoid further
confusion I'd renamed `get_filesystem_encoding` to the less ambiguous
`get_text_file_encoding`.  This commit should complete the transition.