Idle Connection is ignored

[amirhalatzi]

If the connection t/o, or is actively reset, it is not recoverable.

Example scenario:

1. Open a pool of 10 connections
2. Have them idle for a long period of time (1 hour is enough for Windows to close them)
3. Perform a Riak action
   The result: I get 'Unable to access functioning Riak node'.

I'd expect it to detect it before using the network socket, and silently re-opening it.

[peschkaj]

Directly related to #1, #9, and #157

[taliesins]

Half open connections are causing this issue. So if we are going to use connection pooling then we should close connections when they:

• timeout
• socket exception occurs

For an implementation please see:
https://github.com/taliesins/CorrugatedIron/blob/master/CorrugatedIron/Comms/RiakConnectionPool.cs
https://github.com/taliesins/CorrugatedIron/blob/master/CorrugatedIron/Comms/RiakPbcSocket.cs

[peschkaj]

Could you send over a pull request to make review easier?