Add 'exit on success' to examples docs?

[dsummersl]

I wanted to run my test cases (a shell command, it doesn't matter what) and only leave the tmux pane open if the exit code is non-zero (ie, only if there is something exceptional I should look at). Turned out to be super simple, but it took me a bit of time brainstorming to figure it out: just use standard bash!

:VimuxRunCommand('myteststcript && exit')

Thought it might be nice to add an example like this to the docs.

Thanks so much for this plugin; love its straight up single-purposeness.

[alerque]

Sure, I'd be happy to see a blurb about this in the docs for the sake of future users with similar needs. Do you (or anyone seeing this) care to edit the help file and submit it as a PR?