treat 403 as warning instead of error in link checker - #306

Changed pages include:

• index.html - view
• davis/index.html - view
• events/index.html - view
• los-angeles/index.html - view
• news/index.html - view
• oss-resources/index.html - view
• posts/index.html - view
• san-diego/index.html - view
• santa-barbara/index.html - view
• about/about/index.html - view

There are more changes not included in the list