Adding request context to exception message

Prior to this patch, I would receive the following exception:
```
Errno::ECONNREFUSED (Connection refused - connect(2))
```

With this patch, I receive the equivalent of:
```
Errno::ECONNREFUSED: Connection refused - {
  :uri=>#<URI::HTTP:0x007fd5093b22a8 URL:http://localhost/some_uri>,
  :method=>:get,
  :open_timeout=>42
}
``
Merge pull request #54 from jeremyf/adding-connection-information-to-error-handling

Adding request context to exception message