No way to get raw query parameters
As far as I can tell, Jester doesn't provide any way to get the raw query parameters, and the `params` implementation as a string to string mapping is problematic because query keys can be repeated. Here's an example:
```
?field=hi&field=bye
```
In this case, params would just have field:bye. HTML `<select multiple` uses this format to send multiple choices that have been selected, as do checkboxes. Right now, as far as I can tell, it is impossible to have a multiselect without additional javascript to send it as JSON rather than a query string. I could be mistaken, but I glanced through the code and the required variables to do it are private.

PR inbound to just get the query string, similar to the `path` proc.