Move docs in-source (#1357)

docs/Makefile

@@ -0,0 +1,24 @@
+# Minimal makefile for Sphinx documentation
+#
+
+# You can set these variables from the command line.
+SPHINXOPTS    = -W --keep-going
+SPHINXBUILD   = sphinx-build
+SOURCEDIR     = source
+LINTER        = doc8
+LINTEROPTS    = --ignore D001 # D001 is linelength
+BUILDDIR      = build
+
+# Put it first so that "make" without argument is like "make help".
+help:
+	@$(SPHINXBUILD) -M help "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)
+
+lint:
+	@$(LINTER) $(LINTEROPTS) $(SOURCEDIR)
+
+.PHONY: help Makefile
+
+# Catch-all target: route all unknown targets to Sphinx using the new
+# "make mode" option.  $(O) is meant as a shortcut for $(SPHINXOPTS).
+%: Makefile
+	@$(SPHINXBUILD) -M $@ "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)