README: Update recommendation for file-nullbyte to only search text f…

…iles

This updates the recommended / suggested configuration file presented in
the `README.md` file, so that `file-nullbyte` is only searching text
files by default (`FILE_NULLBYTE_TEXT=0).

Searching binary files for null bytes (`NUL`) makes not too much sense,
since it will regularly find such files, and it is perfectly fine for
them to contain these bytes.

This addresses one aspect of an issue with searching binary files with
this particular file check (documented in cytopia#14).

README.md

@@ -282,7 +282,7 @@ FILE_EMPTY_SIZE=0
 # file-nullbyte
 FILE_NULLBYTE_EXTENSION=""
 FILE_NULLBYTE_IGNORE=".git,*.svn,*.pyc"
-FILE_NULLBYTE_TEXT=0
+FILE_NULLBYTE_TEXT=1
 FILE_NULLBYTE_SIZE=1
 
 # file-trailing-newline