remove HTTP check mode and TCP check mode. add ping timeout option.

#### 1. remove HTTP check mode and TCP check mode

HTTP check and TCP port check already exist. these are in security/check-ports.tb and http/check-http.rb

In addition, TCP check mode does not work on internal network.
For example, port 81 is not open in my machines.

```
/opt/sensu/embedded/bin/ruby /etc/sensu/plugins/check-ping.rb -t TCP -h localhost -p 81
```

```
/opt/sensu/embedded/bin/ruby /etc/sensu/plugins/check-ping.rb -t TCP -h 192.168.1.101 -p 81
```

the result below is in both cases.

```
CheckPING OK: TCP ping successful for host: localhost(or 192.168.1.101)
```

I think the result should be NG.


#### 2. Add ping timeout option.

You can set ping timeout using -T option.


I am a beginner in Ruby. I am not knowledgeable about net-ping library.
Please check and tell me if there are any problems.
If you are ok, please merge pull request.

Hiroaki.