command line args could use some documentation

[coke]

The README points to the output of the command, but that doesn't detail what the individual subcommands actually do. It would be nice if we had another markdown file that listed the available options and what they're for.

[RichardJActon]

Hi, a specific instance of this from the usage message is:

rakudobrew switch jvm|moar|moar-blead

when you install a new version using the form:

rakudobrew build jvm|moar|moar-blead|all [tag|branch|sha-1] [--configure-opts=]

you have to switch to it using something of the form:

rakudobrew switch jvm|moar|moar-blead-[tag|branch|sha-1]

e.g. rakudobrew switch moar-2018.04.1

which is not clear from the documentation of the switch option in usage.

see: https://stackoverflow.com/questions/45464233/multiple-versions-of-perl6-using-rakudobrew?utm_medium=organic&utm_source=google_rich_qa&utm_campaign=google_rich_qa

[patrickbkr]

The default help message has changed a bit. The switch command now at least doesn't give wrong instructions. Also the README.md now gives a one-liner explanation for each command there is.
I'll have a look at PR#125 soon-ish.