setup looking for non-existant file

[IanSudbery]

Running setup.py on the lastest pull gives the following error:

Traceback (most recent call last):
  File "setup.py", line 29, in <module>
    with open('xonsh_kernel.py', 'rb') as fid:
FileNotFoundError: [Errno 2] No such file or directory: 'xonsh_kernel.py'

xonsh_kernel is now a directory rather than a self contained file.

[blink1073]

Thanks @IanSudbery, I actually forgot to remove setup.py, I've switched to flit for development.