colors and log
Even if I turn the colors off, xmrig-proxy still shows some colored output on screen.
I don't really care about it on screen, but color codes breaks the log file, example:

```
[2017-08-10 16:34:47] #000 [01;37muse pool [01;36mxmr-eu1.nanopool.org:14444 [01;30m79.137.82.5
[2017-08-10 16:34:47] #000 [01;35mnew job[0m from [01;37mxmr-eu1.nanopool.org:14444[0m diff [01;37m120001
```

As a solution I would appreciate removed ANSI codes in log.

I have in config following setting:
```
"colors": false,
"log-file": "log.log",
```

Please fix. Thank you!