Include missing files in sdist

[thatch]

Include missing files in sdist for #3

Tested with

++ mktemp -d
+ D=/tmp/tmp.Q5gE08bgJZ
+ trap 'rm -rf /tmp/tmp.Q5gE08bgJZ' EXIT
+ python -m venv /tmp/tmp.Q5gE08bgJZ
+ python setup.py sdist -d /tmp/tmp.Q5gE08bgJZ
running sdist
running egg_info
creating dpy_ui.egg-info
writing dpy_ui.egg-info/PKG-INFO
writing dependency_links to dpy_ui.egg-info/dependency_links.txt
writing requirements to dpy_ui.egg-info/requires.txt
writing top-level names to dpy_ui.egg-info/top_level.txt
writing manifest file 'dpy_ui.egg-info/SOURCES.txt'
reading manifest file 'dpy_ui.egg-info/SOURCES.txt'
reading manifest template 'MANIFEST.in'
writing manifest file 'dpy_ui.egg-info/SOURCES.txt'
running check
warning: Check: missing meta-data: if 'author' supplied, 'author_email' must be supplied too

creating dpy-ui-0.2.0
creating dpy-ui-0.2.0/discord
creating dpy-ui-0.2.0/discord/ext
creating dpy-ui-0.2.0/discord/ext/ui
creating dpy-ui-0.2.0/dpy_ui.egg-info
copying files to dpy-ui-0.2.0...
copying MANIFEST.in -> dpy-ui-0.2.0
copying README.md -> dpy-ui-0.2.0
copying requirements.txt -> dpy-ui-0.2.0
copying setup.py -> dpy-ui-0.2.0
copying discord/ext/ui/__init__.py -> dpy-ui-0.2.0/discord/ext/ui
copying discord/ext/ui/helpers.py -> dpy-ui-0.2.0/discord/ext/ui
copying discord/ext/ui/message.py -> dpy-ui-0.2.0/discord/ext/ui
copying discord/ext/ui/paginator.py -> dpy-ui-0.2.0/discord/ext/ui
copying discord/ext/ui/session.py -> dpy-ui-0.2.0/discord/ext/ui
copying discord/ext/ui/version.py -> dpy-ui-0.2.0/discord/ext/ui
copying dpy_ui.egg-info/PKG-INFO -> dpy-ui-0.2.0/dpy_ui.egg-info
copying dpy_ui.egg-info/SOURCES.txt -> dpy-ui-0.2.0/dpy_ui.egg-info
copying dpy_ui.egg-info/dependency_links.txt -> dpy-ui-0.2.0/dpy_ui.egg-info
copying dpy_ui.egg-info/requires.txt -> dpy-ui-0.2.0/dpy_ui.egg-info
copying dpy_ui.egg-info/top_level.txt -> dpy-ui-0.2.0/dpy_ui.egg-info
Writing dpy-ui-0.2.0/setup.cfg
Creating tar archive
removing 'dpy-ui-0.2.0' (and everything under it)
+ cd /
+ /tmp/tmp.Q5gE08bgJZ/bin/pip install /tmp/tmp.Q5gE08bgJZ/dpy-ui-0.2.0.tar.gz
Processing /tmp/tmp.Q5gE08bgJZ/dpy-ui-0.2.0.tar.gz
Installing collected packages: dpy-ui
  Running setup.py install for dpy-ui: started
    Running setup.py install for dpy-ui: finished with status 'done'
Successfully installed dpy-ui-0.2.0
WARNING: You are using pip version 19.2.3, however version 20.1.1 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.
+ echo Success
Success
++ rm -rf /tmp/tmp.Q5gE08bgJZ