WIP: Real-time feedback

- [x] Setting up TCP/IP connection 
- [x] Adding unit tests for TCP/IP connection
- [x] Adding fakebrainresponses() method
- [x] Adding psychopy example

The examples run without errors. Open ipython in two separate terminals. In the first one, run `rt_feedback_server.py` and then wait for the message `RtServer: Start`. Once that appears, (take your own time and) run `rt_feedback_client.py` and the feedback script should start. 

Test coverage
--------------------

```sh
mne.realtime                            4      0   100%   
mne.realtime.client                   166    132    20%   44-63, 68-74, 102-133, 149-171, 184-200, 210-233, 243, 253-263, 267-268, 272, 285-290, 300-305, 316-317, 322-323, 327-328, 343-353, 368-373
mne.realtime.epochs                   143      7    95%   225-229, 393, 395-396
mne.realtime.mockclient                50      2    96%   170, 174
mne.realtime.stim_server_client       107      2    98%   258-259
```

Test timing
----------------

```sh
TOTAL                               16419   6788    59%   
mne.realtime.tests.test_mockclient.test_fakebrainresponse: 0.1059s
mne.realtime.tests.test_stim_client_server.test_connection: 0.5033s
mne.realtime.tests.test_mockclient.test_mockclient: 2.4516s
```

Sub-Issues
----------------
- [x] `mywin.close()` doesn't appear to work
- [x] `logger.info()` prints message twice
- [x] Error `[Errno 98] Address already in use` with `Ctrl + C`
- [x] Small delay after starting client before it starts getting triggers
- [x] Rebase branch w.r.t master