Eradication of `data` arg to requests. We no longer need to pass this
value around as we have a) type inference, b) nested object insertion
via `put` and `append`.
Fix `joinPath` numeric type coercion
Detect empty string params and treat them as blank with expectParams()
Fix error logging/stack trace printing.
Update Zmpl - includes debug tokens + error tracing to source template
in debug builds.
In `main()`:
```zig
app.route(.GET, "/custom/:id/foo/bar", @import("app/views/custom/foo.zig"), .bar);
```
Routes `GET` request with path (e.g.) `/custom/1234/foo/bar` to `bar()`
defined in `src/app/views/custom/foo.zig`.
Routes with an `:id` segment expect a function with three parameters,
routes without an `:id` segment expect a function with two parameters
(i.e. the same as `get` vs `index`).
