improving UX

First of all, thank you for writing such a great package. It has changed the way I work. This package was exactly what I was looking for.

Some of the suggestions here are listed in other issues as well. I have been comparing the user experience in Jupyter notebook and emacs-jupyter and here are a few things that makes Jupyter notebook friendlier. This might be more a feature request than an issue.

• currently running block is marked as such. Solution: Results block has a * for code that is running and number specifying execution order for the once that are completed. May be another symbol to specify if an execution was cancelled.
• blocks are numbered by the order in which this were run Solution: Same as point 1.
• evaluating the entire buffer is more intuitive. When I try to do this in emacs-Jupyter sometimes my results are not displayed Solution: Print a message saying which block interrupted the Kernel and to go to that Kernel. Maybe this is already implemented.
• the currently active block is clearly marked with a blocked blue line on the left. Implementing this might be useful for org-Babel in general. Solution: orgbabel block that is currently active can change color in someway- maybe the ability to set two color schemes for the #+begin and #+end depending on whether the block is active.

Let me know if you agree, disagree or plan to implement any of these.