Installation script failed due to outdated URLs

Please, update the links in installation scripts with HTTP**S** equivalents.

Current situation in Ubuntu 16.04:

```
~# curl -s "http://pixlcore.com/software/simplebot/install-latest-stable.txt"
<html>
<head><title>301 Moved Permanently</title></head>
...

~# curl -V
curl 7.47.0 ...
```
