Send authentication needed header when no user/pw

Foxbrowser does not send a username and password in its first request.
Only upon responding with a ```WWW-Authenticate: Basic``` header the
client sends the username and password in the following request.

See #24.
Remove trailing slash also with URL params

Foxbrowser sends requests for URLs like
```http://example.com/storage/collection/?full=1```. This fix removes
the trailing slash before the question mark to allow for correct
parsing.

See #24.
Merge pull request #86 from owncloud/foxbrowser_fixes

Foxbrowser fixes