Docs fail due to failure to install NumPy

[LeeBergstrand]

Installed /home/docs/checkouts/readthedocs.org/user_builds/pygenprop/envs/latest/lib/python3.7/site-packages/pygenprop-0.8-py3.7.egg
Processing dependencies for pygenprop==0.8
Searching for scikit-bio>=0.5.5
Reading https://pypi.org/simple/scikit-bio/
Downloading https://files.pythonhosted.org/packages/2d/ff/3a909ae8c212305846f7e87f86f3902408b55b958eccedf5d4349e76c671/scikit-bio-0.5.5.tar.gz#sha256=9fa813be66e88a994f7b7a68b8ba2216e205c525caa8585386ebdeebed6428df
Best match: scikit-bio 0.5.5
Processing scikit-bio-0.5.5.tar.gz
Writing /tmp/easy_install-q04fkwzf/scikit-bio-0.5.5/setup.cfg
Running scikit-bio-0.5.5/setup.py -q bdist_egg --dist-dir /tmp/easy_install-q04fkwzf/scikit-bio-0.5.5/egg-dist-tmp-f0kz4d8j
Traceback (most recent call last):
  File "/home/docs/checkouts/readthedocs.org/user_builds/pygenprop/envs/latest/lib/python3.7/site-packages/setuptools/sandbox.py", line 154, in save_modules
    yield saved
  File "/home/docs/checkouts/readthedocs.org/user_builds/pygenprop/envs/latest/lib/python3.7/site-packages/setuptools/sandbox.py", line 195, in setup_context
    yield
  File "/home/docs/checkouts/readthedocs.org/user_builds/pygenprop/envs/latest/lib/python3.7/site-packages/setuptools/sandbox.py", line 250, in run_setup
    _execfile(setup_script, ns)
  File "/home/docs/checkouts/readthedocs.org/user_builds/pygenprop/envs/latest/lib/python3.7/site-packages/setuptools/sandbox.py", line 45, in _execfile
    exec(code, globals, locals)
  File "/tmp/easy_install-q04fkwzf/scikit-bio-0.5.5/setup.py", line 20, in <module>
    url='https://github.com/Micromeda/pygenprop',
ModuleNotFoundError: No module named 'numpy'

This is due to way that skbio was packaged:

scikit-bio/scikit-bio#1671

Solution: Wait until skbio is updated.