Add some feedback to the cli

[MCMic]

Hello, I wanted to try rivalcfg, but it does not work, and there is no error or success message.

I tried: rivalcfg -C "rgbgradient(duration=15000; colors=0%: black, 8%: red, 16%: black, 24%: yellow, 32%: black, 40%: lime, 48%: black, 56%: aqua, 64%: black, 72%: blue, 80%: black, 88%: fuchsia)"

And nothing happenned.
«rivalcfg» with no argument does nothing either, it should either show usage or help, or do something (list devices, maybe this is what it’s doing, but in this case it should explicitely say that no compatible devices were found).

I have a Sensei Ten, I installed rivalcfg from AUR on ArchLinux. I ran the update-dev as root, then unplugged/replugged the device. I did not reboot.
Maybe rivalcfg does not work, maybe I misunderstood how to use it, maybe my gradient syntax from the documentation is wrong, hard to say without any error message.

[flozz]

You are right, rivalcfg should display an "usage" message when no argument is given... I probably forgotten this.

I will look at this next week :)

[flozz]

I added a message that is displayed when no argument was given.

For issues the the Sensei TEN, I will check that in #154 :)