docs: drop sphinx-autobuild, avoids 10 deps (-16%)

sphinx-autobuild==0.6.0 (from -r docs/docs-requirements.txt (line 2))
livereload>=2.3.0 (from sphinx-autobuild==0.6.0->-r docs/docs-requirements.txt (line 2))
pathtools>=0.1.2 (from sphinx-autobuild==0.6.0->-r docs/docs-requirements.txt (line 2))
tornado>=3.2 (from sphinx-autobuild==0.6.0->-r docs/docs-requirements.txt (line 2))
argh>=0.24.1 (from sphinx-autobuild==0.6.0->-r docs/docs-requirements.txt (line 2))
watchdog>=0.7.1 (from sphinx-autobuild==0.6.0->-r docs/docs-requirements.txt (line 2))
port-for==0.3.1 (from sphinx-autobuild==0.6.0->-r docs/docs-requirements.txt (line 2))
backports.ssl_match_hostname (from tornado>=3.2->sphinx-autobuild==0.6.0->-r docs/docs-requirements.txt (line 2))
singledispatch (from tornado>=3.2->sphinx-autobuild==0.6.0->-r docs/docs-requirements.txt (line 2))
backports_abc>=0.4 (from tornado>=3.2->sphinx-autobuild==0.6.0->-r docs/docs-requirements.txt (line 2))

docs/Makefile

@@ -2,7 +2,7 @@
 #
 
 default:
-	sphinx-autobuild -b html $(ALLSPHINXOPTS) $(BUILDDIR)/html
+	sphinx-autobuild . build/html/
 
 # You can set these variables from the command line.
 SPHINXOPTS    =

docs/docs-requirements.txt

@@ -1,4 +1,3 @@
 Sphinx==1.7.1
-sphinx-autobuild==0.6.0 # Last version to support Python 2.6
 sphinxcontrib-programoutput==0.11
 alabaster==0.7.10