Fix for Names Bug

Moves member pages to use a canonical form of `/mp/{id}/member_name`, where only the ID is relevant to determining which member to display.

* Fixes #20.
* Fixes #122.

## To Do

* [x] Make URL routing handle canonical (numerical) addresses elegantly.
* [x] Stop canonical ID handling page from redirecting back to name-only URL.
* [x] Stop locations referencing the name-only URLs.
* [x] Tests to ensure URL generation behaves in a sane manner from now on.