docs: Generate README.rst to work around GitHub not rendering `.. include::` in rst files.

This work might look like extensive for just fixing a small issue like
the include rendering, but it will all be heavily reused by the
skywater-pdk scripts that will be released soon.

This commit;
 - Adds Makefile for creating a self contained conda environment under
   `env/conda`

 - Installs required Python dependencies into the environment (which is
   currently just the `rst_include` tool).

 - Has a Makefile to generate `README.rst` from `README.src.rst`

 - Has Travis CI run on repository and check that the `README.rst` file
   has been rebuilt and committed if any of the dependencies have
   change.

Signed-off-by: Tim 'mithro' Ansell <tansell@google.com>
diff --git a/docs/versioning.rst b/docs/versioning.rst
index a252669..294e216 100644
--- a/docs/versioning.rst
+++ b/docs/versioning.rst
@@ -1,5 +1,5 @@
-Version Numbering
------------------
+Version Number Format
+---------------------
 
 Version numbers for both the PDK and the supplied libraries are fully specified by a 3-digit version number followed by a git commit count and a git commit short hash.