Reduce warnings and errors in sample content

This reduces the warnings and errors when generating the sample content
from twelve to one (intentional) warning. The latter is expected by
assertLogCountEqual() in the "test_basic_generation_works" test.

samples/pelican.conf.py

@@ -40,13 +40,16 @@ EXTRA_PATH_METADATA = {
 
 # static paths will be copied without parsing their contents
 STATIC_PATHS = [
-    'pictures',
+    'images',
     'extra/robots.txt',
     ]
 
 # custom page generated with a jinja2 template
 TEMPLATE_PAGES = {'pages/jinja2_template.html': 'jinja2_template.html'}
 
+# there is no other HTML content
+READERS = {'html': None}
+
 # code blocks with line numbers
 PYGMENTS_RST_OPTIONS = {'linenos': 'table'}