* Clarify pathname docs, follow spec with fragments
- Valid URLs must not contain a `#` within its fragment.
https://github.com/MithrilJS/mithril.js/issues/2445
- Our docs were a little confusing and misleading - `m.pathname` isn't
aware of URLs, just path names.
- Removed the relevant extension to `m.parseQueryString` required to
support the hash parsing extension. Now we just shave it off and
ignore it.
- Fix support for arbitrary prefixes, so prefixes like `?#` are
handled correctly.
- Add a bunch of tests to cover various areas of confusion and unusual
edge cases.
* Update with PR [skip ci]
