Fix for failing tests

2 changes are included:
* About 4 months ago the VirtualSocket class was changed to require a new parameter for the __init__ function - a dictionary of configuration parameters like heartbeat timeout. The tests were not updated to pass this parameter and were failing.
CHANGE: Pass an empty dictionary, as the tests don't need any special configuration.

* Fix logic in 3 failing tests
  * Test "test_incr_hist" was calling incr_hist() and expecting connection state to change from NEW to CONNECTED. But that function makes no change to connection state. So either the incr_hists() function needs to set the connection state to CONNECTED if ever called (doesn't seem right) or the test needs to set the state and then check it is unchanged after. This is a judgment call - the change could be made either way: fix the incr_hist() code to update connection status, or change the test to set status.
  * Test "test_disconnect" was calling disconnect() on the socket, then verifying the state was still CONNECTED. Calling disconnect() should result in a state of DISCONNECTING.
  * Fix an issue with "test_encode_json_decimals" with Python 2.6. Need to convert float to str before converting to Decimal.

With this patch, tests will be passing again. I would love to see the travis-ci indicator with green - it indicates a healthy project and will encourage more use.