docs warnings as errors and initial page similar to README

* Changed "index" to be more similar to the README (#1708).
* Fixes numerous issues like missing documents, syntax errors, etc (#1829, #432).
* Mention all docs in "contents.rst" so it's easier for users to locate (#1112).
* Add doc generation and checking to Travis and AppVeyor, to avoid re-introducing errors.

Fixes #432, Fixes #1112, Fixes #1708, Fixes #1829

.travis.yml

@@ -26,6 +26,7 @@ env:
     - TESTENV=py27-nobyte
     - TESTENV=doctesting
     - TESTENV=freeze
+    - TESTENV=docs
 
 script: tox --recreate -e $TESTENV