Updated to Sphinx 1.3 to allow using :any: to reference vars.

Refer to the [Sphinx documentation about `:any:`](http://www.sphinx-doc.org/en/stable/markup/inline.html#role-any)
`:any:` can be used in Sphinx to reference variables. Example:

```YAML
ferm__enabled: True

ferm__flush: '{{ ferm__enabled | bool }}'
```

When using this, we might need to adjust sections names. Example:

```reStructuredText
.. _ferm_input_list:

ferm_input_list
---------------
```

could be changed to:

```reStructuredText
.. _ferm_detailed_input_list:

ferm_input_list
---------------
```

1.3.4 has been chosen because it is the current version in [jessie-backports](https://packages.debian.org/jessie-backports/python-sphinx).

.travis.yml

@@ -5,7 +5,7 @@ python:
   - "2.7"
 
 # command to install dependencies
-install: "pip install -q yaml2rst sphinx==1.2.2"
+install: "pip install -q yaml2rst sphinx==1.3.4"
 
 # command to run tests
 script: ./test.sh -W