Split requirements for RTD documentation build into separate extra (#41)

Since these are not core requirements of the Sphinx parser.

.circleci/config.yml

@@ -11,7 +11,7 @@ jobs:
       - restore_cache:
           keys:
             - cache-pip
-      - run: pip install --user -e .[testing,sphinx]
+      - run: pip install --user -e .[sphinx,rtd]
       - save_cache:
           key: cache-pip
           paths:

.readthedocs.yml

@@ -7,3 +7,4 @@ python:
         path: .
         extra_requirements:
           - sphinx
+          - rtd

docs/index.md

@@ -20,7 +20,7 @@ Or for package development:
 git clone https://github.com/chrisjsewell/mistletoe
 cd mistletoe
 git checkout myst
-pip install -e .[sphinx,testing]
+pip install -e .[sphinx,code_style,testing,rtd]
 ```
 
 This should install the myst fork of mistletoe, along with the Sphinx parser

setup.py

@@ -40,6 +40,7 @@
         )
     ],
     extras_require={
+        "sphinx": ["pyyaml", "docutils>=0.15", "sphinx>=2,<3"],
         "code_style": ["flake8<3.8.0,>=3.7.0", "black", "pre-commit==1.17.0"],
         "testing": [
             "coverage",
@@ -48,13 +49,7 @@
             "pytest-regressions",
             "beautifulsoup4",
         ],
-        "sphinx": [
-            "pyyaml",
-            "docutils>=0.15",
-            "sphinx>=2,<3",
-            "sphinxcontrib-bibtex",
-            "ipython",
-        ],
+        "rtd": ["sphinxcontrib-bibtex", "ipython"],
     },
     zip_safe=True,
 )