catch error message from hipchat-api response

I have add a new feature for this plugin.
It comes to catch and raise message on response error such as these error below.

* too log message
* invalid from name

### example of error behavior

```
2014-02-19 12:03:18 +0900 hipchat.message: {"from":"<abc>","message":"test"}
2014-02-19 12:03:21 +0900 [error]: HipChat Error: error_class=StandardError error="From name may not contain HTML."
```

```
2014-02-19 12:03:27 +0900 hipchat.message: {"from":"user@example.com","message":"test"}
2014-02-19 12:03:29 +0900 [error]: HipChat Error: error_class=StandardError error="From name must be between 1 and 15 characters."
```