Fix rescue exceptions in capistrano integration

When I set invalid color to `hipchat_color` like below, I got `NameError`

```
# deploy.rb
set :hipchat_color,          'invalid-color'
```

```
$ cap deploy
...
* 2013-07-16 11:51:58 executing `hipchat:notify_deploy_finished'
/Users/fukayatsu/.rbenv/versions/2.0.0-p195/lib/ruby/gems/2.0.0/gems/hipchat-0.10.1/lib/hipchat/capistrano.rb:68:in `rescue in block in send': uninitialized constant UnknownRoom (NameError)
	from /Users/fukayatsu/.rbenv/versions/2.0.0-p195/lib/ruby/gems/2.0.0/gems/hipchat-0.10.1/lib/hipchat/capistrano.rb:66:in `block in send'
	from /Users/fukayatsu/.rbenv/versions/2.0.0-p195/lib/ruby/gems/2.0.0/gems/hipchat-0.10.1/lib/hipchat/capistrano.rb:65:in `each'
	from /Users/fukayatsu/.rbenv/versions/2.0.0-p195/lib/ruby/gems/2.0.0/gems/hipchat-0.10.1/lib/hipchat/capistrano.rb:65:in `send'
	from /Users/fukayatsu/.rbenv/versions/2.0.0-p195/lib/ruby/gems/2.0.0/gems/hipchat-0.10.1/lib/hipchat/capistrano.rb:42:in `block (3 levels) in <top (required)>'
	...
```