Prohibit positional bool

[CreepySkeleton]

Closes #212

cc @TeXitoi please also take a look at #292

[therealprof]

The example is good, the "documentation" does not help a bit.

[CreepySkeleton]

@therealprof The doc is to address #287 , your case is covered by the example.

[therealprof]

Well, it didn't say that on the label, maybe you should throw in a "Closes #287" then?

[CreepySkeleton]

@therealprof
#287 is not an issue but PR, take look at the first comment there for detailed information.
I included it in this PR because "see this for example" link refers to examples/true_or_false.rs which is yet to be added by this PR.

[CreepySkeleton]

The example is good, the "documentation" does not help a bit.

Also, @therealprof , if you have some idea about how to address your case in the doc I'm all ears.

[CreepySkeleton]

@therealprof

I would like to apologize for being too blunt. I'm not really a "public relations" man, I take strait approach when explaining thinks to others, too strait sometimes. It was never my intention to offend you or discard your opinion, sorry if I left wrong impression.

But I'm not making amends, I mean every word I said. I still believe you case is a corner one, true/false arguments are common for config files indeed, but I have yet to meet a case when I would need to actually use them on command line. Even more, I wasn't even aware of existence of such applications until after you'd brought some examples.

We can't bring every corner case to README (and it's not an actual documentation anyway), hence I'm closing your PR. Do you think this PR provides adequate explanation?

@TeXitoi could use a review

[TeXitoi]

Great!

[therealprof]

@CreepySkeleton No worries, all good here.