ENH: Added sphinx documentation pages

docs/source/feature.rst

+Feature
+=========================================
+.. toctree::
+   :maxdepth: 2
+   :titlesonly:
+   :caption: Contents:
+
+
+.. automodule:: ml.feature
+    :members:
+    :special-members: __init__

docs/source/identifier.rst

+Identifier
+=========================================
+.. toctree::
+   :maxdepth: 2
+   :titlesonly:
+   :caption: Contents:
+
+
+.. automodule:: ml.identifier
+    :members:
+    :special-members: __init__

docs/source/index.rst

@@ -15,6 +15,9 @@ Table of Contents
 
    md/preliminaries.md
    thing
+   feature
+   identifier
+   role
    dt_factory
    tools
 

docs/source/role.rst

+Role
+=========================================
+.. toctree::
+   :maxdepth: 2
+   :titlesonly:
+   :caption: Contents:
+
+
+.. automodule:: ml.role
+    :members:
+    :special-members: __init__