use make html instead of sphinx-build and add make check

.gitignore

@@ -1,4 +1,4 @@
 .direnv
 .envrc
-build
+_build
 *~

Makefile

@@ -151,3 +151,5 @@ doctest:
 	$(SPHINXBUILD) -b doctest $(ALLSPHINXOPTS) $(BUILDDIR)/doctest
 	@echo "Testing of doctests in the sources finished, look at the " \
 	      "results in $(BUILDDIR)/doctest/output.txt."
+
+check: html

development.rst

@@ -90,8 +90,8 @@ Build the documentation
 
 1. Build::
 
-     $ sphinx-build -b html . build/html
+     $ make html
 
 2. Display::
 
-     $ firefox build/html/index.html
+     $ firefox _build/html/index.html