vwtags: Drop help and import from __future__

We don't need the help message as g:tagbar_type_vimwiki is set by
taskwiki itself, and as we're going to refactor this, maintaining the
help is extra work that makes little sense here.

The import isn't needed in python3.

extra/vwtags.py

@@ -1,37 +1,10 @@
 #! /usr/bin/env python3
 # -*- coding: utf-8 -*-
 
-from __future__ import print_function
-
-help_text = """
-Extracts tags from Vimwiki files. Useful for the Tagbar plugin.
-
-Usage:
-Install Tagbar (http://majutsushi.github.io/tagbar/). Then, put this file
-anywhere and add the following to your .vimrc:
-
-let g:tagbar_type_vimwiki = {
-          \   'ctagstype':'vimwiki'
-          \ , 'kinds':['h:header']
-          \ , 'sro':'&&&'
-          \ , 'kind2scope':{'h':'header'}
-          \ , 'sort':0
-          \ , 'ctagsbin':'/path/to/vwtags.py'
-          \ , 'ctagsargs': 'default'
-          \ }
-
-The value of ctagsargs must be one of 'default', 'markdown' or 'media',
-whatever syntax you use. However, if you use multiple wikis with different
-syntaxes, you can, as a workaround, use the value 'all' instead. Then, Tagbar
-will show markdown style headers as well as default/mediawiki style headers,
-but there might be erroneously shown headers.
-"""
-
 import sys
 import re
 
 if len(sys.argv) < 3:
-    print(help_text)
     exit()
 
 syntax = sys.argv[1]