Pluses get replaced with spaces

**I'm submitting a bug report**

* **Library Version:**
1.1.3

**Please tell us about your environment:**
* **Operating System:**
Windows 10

* **Node Version:**
8.9.4

* **NPM Version:**
6.9.0

* **JSPM OR Webpack AND Version**
webpack 4.30.0

* **Browser:**
all

* **Language:**
all

**Current behavior:**
Passing `+` in a url parameter results in an argument to `activate` function where `+` is replaced with `[space]`

**Expected/desired behavior:**

* **What is the expected behavior?**
`+` is passed as is

* **What is the motivation / use case for changing the behavior?**
Previously, a path would be passed unencoded which correctly translated to view parameters. Now, when the `+` appears in the path, the line https://github.com/aurelia/path/blob/0be13f7710ddc81def93edaafd6ad3d339077c1d/src/index.js#L229 replaces it with a space.
This breaks scenarios with Asp.Net Identity password reset codes for example.