Match lowercase subdomain against lowercase username

Fixes #30

There are two important parts in a URL for web servers to consider, which have slightly different rules:

 1. **Subdomain**: Everything after `://` until the next `/`. The `mail.google.come` in `https://mail.google.com/mail/u/0/#inbox`.
 2. **Path**: Everything after and including that `/` until a `#` if there is one. `/mail/u/0/` for my inbox. The `#inbox` is not sent by the web browser to the server.

Subdomains have stricter rules on allowed characters and they are case-insensitive. Chromium will actually convert all alpha characters to lowercase before sending the request.

On commit--blog, each blogger gets a subdomain for their blog, and that subdomain comes from their username. Until this past Tuesday, everyone who I've convinced to sign up and try it out has had all-lowercase usernames. @pR0Ps finally bucked the trend and uncovered this issue.

The fix is simple: query the lowercased subdomain against lowercased usernames. Woo.

[Wikipedia on URLs](https://en.wikipedia.org/wiki/Url). There is a lot there. Always interesting to find out new things that seem very familiar.