Try to fix readthedocs

.readthedocs.yml

@@ -1,3 +1,2 @@
-requirements_file: docs/requirements.txt
 conda:
   file: docs/environment.yml

docs/environment.yml

@@ -1,3 +1,67 @@
 name: slack-sansio-doc
 dependencies:
   - python=3.7
+  - pip:
+    - aiohttp==3.4.4
+    - alabaster==0.7.12
+    - appdirs==1.4.3
+    - asks==2.2.0
+    - async-generator==1.10
+    - async-timeout==3.0.1
+    - asynctest==0.12.2
+    - atomicwrites==1.2.1
+    - attrs==18.2.0
+    - Babel==2.6.0
+    - black==18.9b0
+    - certifi==2018.10.15
+    - chardet==3.0.4
+    - Click==7.0
+    - coverage==4.5.2
+    - curio==0.9
+    - docutils==0.14
+    - filelock==3.0.10
+    - flake8==3.6.0
+    - h11==0.8.1
+    - idna==2.7
+    - imagesize==1.1.0
+    - isort==4.3.4
+    - Jinja2==2.10
+    - MarkupSafe==1.1.0
+    - mccabe==0.6.1
+    - mock==2.0.0
+    - more-itertools==4.3.0
+    - multidict==4.5.0
+    - multio==0.2.4
+    - mypy==0.641
+    - mypy-extensions==0.4.1
+    - outcome==1.0.0
+    - packaging==18.0
+    - pbr==5.1.1
+    - pluggy==0.8.0
+    - py==1.7.0
+    - pycodestyle==2.4.0
+    - pyflakes==2.0.0
+    - Pygments==2.2.0
+    - pyparsing==2.3.0
+    - pytest==4.0.0
+    - pytest-asyncio==0.9.0
+    - pytest-cov==2.6.0
+    - pytest-cover==3.0.0
+    - pytest-coverage==0.0
+    - pytz==2018.7
+    - requests==2.20.1
+    - six==1.11.0
+    - sniffio==1.0.0
+    - snowballstemmer==1.2.1
+    - sortedcontainers==2.0.5
+    - Sphinx==1.8.2
+    - sphinxcontrib-asyncio==0.2.0
+    - sphinxcontrib-websupport==1.1.0
+    - toml==0.10.0
+    - tox==3.5.3
+    - trio==0.9.0
+    - typed-ast==1.1.0
+    - urllib3==1.24.1
+    - virtualenv==16.1.0
+    - websocket-client==0.54.0
+    - yarl==1.2.6