Add sphinx and sphinxcontrib-httpdomain

Packages required only to generate the documentation.
They shouldn't really be in the final docker image but they are not very
big and it makes it much easier to generate the doc.

environment.yml

@@ -3,17 +3,21 @@ channels:
 - conda-forge
 - defaults
 dependencies:
+- alabaster=0.7.10=py36_1
 - alembic=0.9.6=py_0
 - asn1crypto=0.22.0=py36_0
+- babel=2.5.1=py36_0
 - blinker=1.4=py_0
 - ca-certificates=2017.11.5=0
 - certifi=2017.11.5=py36_0
 - cffi=1.10.0=py36_0
+- chardet=3.0.4=py36_0
 - click=6.7=py36_0
 - colorama=0.3.9=py36_0
 - coverage=4.4.2=py36_0
 - cryptography=2.0.3=py36_0
 - dnspython=1.15.0=py_0
+- docutils=0.14=py36_0
 - email_validator=1.0.2=py_0
 - factory_boy=2.8.1=py36_0
 - faker=0.8.1=py_0
@@ -28,6 +32,7 @@ dependencies:
 - freetype=2.7=2
 - icu=58.2=0
 - idna=2.6=py36_1
+- imagesize=0.7.1=py36_0
 - itsdangerous=0.24=py_2
 - jansson=2.7=0
 - jinja2=2.9.6=py36_0
@@ -53,20 +58,30 @@ dependencies:
 - pyasn1=0.3.7=py_0
 - pycparser=2.18=py36_0
 - pycrypto=2.6.1=py36_1
+- pygments=2.2.0=py36_0
 - pyjwt=1.5.3=py_0
+- pyopenssl=17.4.0=py36_0
+- pysocks=1.6.8=py36_1
 - pytest=3.2.5=py36_0
 - pytest-cov=2.5.1=py36_0
 - python=3.6.3=1
 - python-dateutil=2.6.1=py36_0
 - python-editor=1.0.3=py36_0
+- pytz=2017.3=py_2
 - qrcode=5.3=py36_0
 - readline=6.2=0
 - redis-py=2.10.6=py_0
+- requests=2.18.4=py36_1
 - setuptools=36.7.2=py36_0
 - six=1.11.0=py36_1
+- snowballstemmer=1.2.1=py36_0
+- sphinx=1.6.7=py36_0
+- sphinxcontrib-websupport=1.0.1=py36_0
 - sqlalchemy=1.1.13=py36_0
 - sqlite=3.13.0=1
 - tk=8.5.19=2
+- typing=3.6.2=py36_0
+- urllib3=1.22=py36_0
 - uwsgi=2.0.15=py36_2
 - werkzeug=0.12.2=py_1
 - wheel=0.30.0=py36_2
@@ -87,6 +102,7 @@ dependencies:
   - flask-session==0.3.1
   - inflection==0.3.1
   - pytest-factoryboy==1.3.1
+  - sphinxcontrib-httpdomain==1.6.0
   - sqlalchemy-citext==1.3.post0
   - sqlalchemy-continuum==1.3.3
   - sqlalchemy-utils==0.32.21