Topic Handler with an invalid Kind attribute causes silent crash

I'm new to defining a topic handler, my first attempt was to use HipChat. I couldn't find specific documentation for defining a topic handler for HipChat so I made my best guess. My initial handler spec file was:

```yaml
---
kind: hipChat
match: changed() == TRUE
options:
room: "influx-notifications"
...
```

I chose "hipChat" because that is the way the node is capitalized on the alert node in TICK script. However, the configuration for HipChat is "hipchat" in all lowercase. After adding this to kapacitor it would seemingly crash and get restarted each time an alert was generated.

When defining a topic handler, the spec file Kind attribute should be validated to help users know what the valid Kind values are, and more importantly not crash kapacitor if there is some problem with it.