Cleanup

- Use doc8 to check rst files
- Add spellcheck and VOLTHA-specific dictionary, fix spelling
- Other formatting and content fixes

Change-Id: I1eea3ab6eba4ec34af0788a681f1e8cd258ea988
diff --git a/requirements.txt b/requirements.txt
index 340b706..4f5937c 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,17 +1,18 @@
 Sphinx~=1.8.5
 actdiag~=0.5.4
 blockdiag~=1.5.4
+doc8~=0.8.0
 livereload~=2.6.1
 nwdiag~=1.0.4
 recommonmark~=0.6.0
-rstcheck~=3.3.1
 seqdiag~=0.9.6
 sphinx-reload~=0.2.0
 sphinx-rtd-theme~=0.4.3
 sphinxcontrib-actdiag~=0.8.5
 sphinxcontrib-blockdiag~=1.5.5
 sphinxcontrib-nwdiag~=0.9.5
-sphinxcontrib-seqdiag~=0.8.5
 sphinxcontrib-openapi~=0.5.0
+sphinxcontrib-seqdiag~=0.8.5
+sphinxcontrib-spelling~=4.2.1
 # sphinx-autoapi~=1.2.1
 # sphinxcontrib-golangdomain