Generate TOC in README

and assert it is up to date

runtests

@@ -18,7 +18,8 @@ def main(sysargs=sys.argv[:]):
     targets = {
         'vet': _vet,
         'test': _test,
-        'gfmxr': _gfmxr
+        'gfmxr': _gfmxr,
+        'toc': _toc,
     }
 
     parser = argparse.ArgumentParser()
@@ -62,6 +63,11 @@ def _vet():
     _run('go vet ./...'.split())
 
 
+def _toc():
+    _run(['node_modules/.bin/markdown-toc', '-i', 'README.md'])
+    _run(['git', 'diff', '--quiet'])
+
+
 def _run(command):
     print('runtests: {}'.format(' '.join(command)), file=sys.stderr)
     check_call(command)