Add documentation to the README

README.rst

@@ -470,6 +470,53 @@ Here are the 5 steps to setup a Deployment dashboard in Buildbot Travis.
            ${stage} is the retrieved from the Deployment dashboard.
            ${version} is retrieved from the Deployment dashboard.
 
+Configuring Travis Defaults
+===========================
+
+The YAML file or Python dict passed to ``TravisConfigurator`` supports a few keys to set some environment defaults.
+
+Default Matrix
+--------------
+The ``default_matrix`` key contains the default values for any keys the repository's ``.travis.yml`` does not specify.
+
+Example::
+
+    default_matrix:
+      os: linux
+      dist: debian_7
+      language:
+        python: 2.7
+        c:
+          compiler: gcc
+        c++:
+          compiler: g++
+
+This example sets the default ``os`` to ``linux``, the default ``dist`` to ``debian_7``, and sets default values for three languages.
+If the ``.travis.yml`` has ``language: c``, then it will have ``compiler`` set to ``gcc``.
+
+Job Options
+-----------
+The ``job_options`` key supports adding properties to a build based on its values.
+An example would be to use one image for Python projects and a different image for JavaScript projects.
+The below example will set the ``image`` property to some UUID for a debian_7 build for C or Python.
+
+Example::
+
+    job_options:
+      linux:
+        debian_7:
+          c:
+            properties:
+              image: 7c6520af-7cf0-46a7-8e15-c30881dde467
+          python:
+            properties:
+              image: bc654b68-4b55-4e1e-a0d2-29d21339600d
+
+The ``job_options`` key must follow a particular format.
+The first level is the ``os``, the second level is the ``dist``, and the third level is the ``language``.
+The value of the final level must be a dict.
+If there is a ``properties`` key, all of the properties within that dict will be added to the build when it is triggered.
+
 How it works
 ============