Do not crash on toConsole when kind is not known

[5p4k]

This fixes #195 and perhaps will prevent crashes in the future, should the node kind not be known.

This PR doesn't even attempt to properly support concepts, just allows the documentation building process to go through.

[florianhumblot]

I think @svenevs put his comment on the wrong PR

Thank you for taking time to try and contribute back to this project!
I will try and look at what to do about concepts this weekend. I have a completely overloaded week though :S
I may be willing to merge it without tests, will have to consider...

is what he said on #201

[svenevs]

I apologize for being stubborn on not letting this hard-fail be relaxed. That said, I thought I was going to archive this repo by now, but it is still something people want. I did the same thing to interface users (PHP, java, etc), but never had the bandwidth to expand support.

Exhale is and always will be C++ first. I will get concepts in, rather than continuing to sit on this. It will need tests, but I will be less strict on getting all cases covered. I just need to "see it to believe it" before I can merge anything. I am somewhat convinced that this is the only reason this repo actually still works as advertised, but will also admit fully that some of the tests are absolutely absurd.

Point is, I'm sorry for the long delay on this, I'm going to try and push concepts through during the next release.