Add urllib3 transport (#14)

diff --git a/docs/reference/google.auth.compute_engine.rst b/docs/reference/google.auth.compute_engine.rst
new file mode 100644
index 0000000..9bf9866
--- /dev/null
+++ b/docs/reference/google.auth.compute_engine.rst
@@ -0,0 +1,8 @@
+google.auth.compute_engine package
+==================================
+
+.. automodule:: google.auth.compute_engine
+    :members:
+    :undoc-members:
+    :show-inheritance:
+
diff --git a/docs/reference/google.auth.rst b/docs/reference/google.auth.rst
index 0f147e9..ef0d689 100644
--- a/docs/reference/google.auth.rst
+++ b/docs/reference/google.auth.rst
@@ -11,6 +11,7 @@
 
 .. toctree::
 
+    google.auth.compute_engine
     google.auth.transport
 
 Submodules
diff --git a/docs/reference/google.auth.transport.rst b/docs/reference/google.auth.transport.rst
index 88b427c..7066334 100644
--- a/docs/reference/google.auth.transport.rst
+++ b/docs/reference/google.auth.transport.rst
@@ -6,3 +6,10 @@
     :undoc-members:
     :show-inheritance:
 
+Submodules
+----------
+
+.. toctree::
+
+   google.auth.transport.urllib3
+
diff --git a/docs/reference/google.auth.transport.urllib3.rst b/docs/reference/google.auth.transport.urllib3.rst
new file mode 100644
index 0000000..32de225
--- /dev/null
+++ b/docs/reference/google.auth.transport.urllib3.rst
@@ -0,0 +1,7 @@
+google.auth.transport.urllib3 module
+====================================
+
+.. automodule:: google.auth.transport.urllib3
+    :members:
+    :undoc-members:
+    :show-inheritance: