Add swarm guide to /docs (#1513)

* docs: add swarm-guide

* readthedocs build configuration file

docs/swarm-guide/README.md

@@ -0,0 +1,25 @@
+# Swarm Guide
+
+Swarm's documentation in sphinx, hosted on read the docs:
+http://swarm-guide.readthedocs.io
+
+## Building the source
+
+After building the source you will find `index.html` in `./build/html/` folder.
+
+### Requirements
+
+- GNU Make
+- Docker or Python (pip)
+
+### Using Docker
+
+After you have `docker` available just call `make html-docker`.
+
+### Native with Python
+
+Execute
+```
+pip install -r requirements.txt
+make html
+```