Store richer information

[beechnut]

Right now we store the assessment of whether the site is up or down, and the timestamp. That means we're throwing away a lot of potentially useful information, like:

• HTTP status codes
• curl exit codes
• the URL being pinged
• the URL we're redirected to

We don't necessarily have a use for all this information right now, and I'm hesitant to give a blanket "more information is better". But up/down determinations are less useful than the status codes. You can have reasonable disagreements over whether a status code means up or down, so I think at least we should keep the status code.

Acceptance criteria:

• Store the HTTP status code, and switch on the code to display up/down information.
• Display status code information in the tooltip.

[beechnut]

I added the HTTP status code in the last commit, closing.