Server responds with 404 if runner name contains a slash

sample_runner.json
```
{
"name" : "I contain a slash /",
...
}
```

Log:

```
2019-10-09 00:39:07,962 [tornado.access.WARNING] 404 GET /scripts/I%20contain%20a%20slash%20/ (46.33.214.58) 1.04ms
```