Issues with running iruby on Fedora 26 (and workaround)

This is less of a bug report and more of an "if you see this, try this:".

I tried following the readme, and (after getting nothing at all from the kernel) finally got "Unknown message type" for message type is_complete_request.

I futzed around a bit after that and got nowhere.

I even tried the docker image described in #115 which failed, saying "ImportError: No module named 'jupyter_console'" (which I had actually managed to work around once before). This indicates, to me at least, that the issue isn't Fedora-specific, given that the docker image is built on an apt-based OS.

Amusingly enough, manually running through the steps in the docker file from #115 gave me a working iruby, after replacing 'ipython' with 'ipython3' in command.rb, to wit:

git clone --depth=1 https://github.com/zeromq/libzmq
git clone --depth=1 https://github.com/zeromq/czmq
cd libzmq && ./autogen.sh && ./configure && make
sudo make install
cd ../czmq && ./autogen.sh && ./configure && make
make install
gem install cztop specific_install
gem specific_install https://github.com/SciRuby/iruby.git

I can't speak to whether that would work generally; I don't know what state my system is in now, re: jupyter/ipython/ruby/iruby

Start with command.rb and the Docker image described in issue #115, then reproduce the is_complete_request and missing jupyter_console errors on Fedora 26 and in the image. Compare the working manual setup, including the ipython3 substitution, with the documented setup; done means the README or relevant commands reliably produce a working iruby kernel.