Resolve "bump up version command doesn't work on MacOS"

Closes #651 (closed).

I thought this was an easy fix in shell, but ended up migrating everything to Ruby. This should be portable enough.

The problem manifested in FreeBSD 13 too. Tested on Linux and in FreeBSD 13 and it works on both. Preferably review this on a MacOS.

I tried to minimize duplicate code. Created task bump at first. Then realized this could have been a simple function and not available to the end user, but I left it like that in the end. I have no strong preference regarding this matter. So now rake bump[1.1.0] is a possible task.

This MR also contains an extra change of restarting nginx when deploying the demo. nginx needing a restart was something that fixed the demo recently.