Allow users to create issues without giving us oauth access.

https://github.com/webcompat/webcompat.com/pull/

So if you a) don't trust us or b) don't have a GitHub account, you can still report a bug. @GIGANTOR will report an issue on your behalf.

(just reminded myself that we probably want to link to the repo as well in the form somewhere)

This closes #46, functionality-wise.