Added README for documentation.

doc/README.md

+# Documentation for m-unit-tests Dynare module
+
+The documentation is written with sphinx, so you need to have
+[Python](https://www.python.org/) on your system with
+[sphinx](http://sphinx-doc.org/). You also need to install the [Read
+the docs](https://readthedocs.org/) theme and the sphinx matlab
+domain, this can be done with pip in a terminal:
+
+```
+ ~$ pip install sphinx_rtd_theme
+ ~$ pip install sphinxcontrib-matlab
+```
+
+To obtain the documentation as an html file in subfolder
+```build/html``` you just have to use the provided Makefile:
+
+```
+ ~$ make html
+```
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