Kill connecting process when exiting Vim

[fixje]

After closing vim, there still exists a process which was spawned by the plugin if the kernel was not terminated with ":IPythonTerminate":

Steps to reproduce:

• start an ipython kernel
• open vim and connect via :IPython
• optional: terminate kernel from outside vim
• close vim

$ ps aux | grep ipython fixje 14513 0.2 0.4 591408 36236 pts/3 Sl 00:49 0:00 /usr/bin/python2 -c from IPython.zmq.ipkernel import main; main() -f /home/fixje/.ipython/profile_default/security/kernel-14508.json --KernelApp.parent_appname='ipython-console' --parent=1