[fix #28] Really use URL encoding function

The previous "fix" commit (aa9e9c7fb0f53b304f2df7783ec9e19b971631a7)
added URL encoding handling. However, this function was not called
in one case: when there is a conflict and the server sends back
its version of the document.

In this commit, we:
- Add the missing call.
- Add corresponding unit test.
- Fix encoding function name.

Closes #28