Adds documentation for Javelin

I followed what's done for the cleanup.py script and re-used parts of
what was described in the javelin spec.

Change-Id: I57adc3764e75784d4614b6c03996433a4ee4332f
diff --git a/doc/source/index.rst b/doc/source/index.rst
index bc4fc46..1f06bc5 100644
--- a/doc/source/index.rst
+++ b/doc/source/index.rst
@@ -37,6 +37,7 @@
    :maxdepth: 1
 
    cleanup
+   javelin
 
 ==================
 Indices and tables
diff --git a/doc/source/javelin.rst b/doc/source/javelin.rst
new file mode 100644
index 0000000..01090ca
--- /dev/null
+++ b/doc/source/javelin.rst
@@ -0,0 +1,5 @@
+----------------------------------------------------------
+Javelin2 - How to check that resources survived an upgrade
+----------------------------------------------------------
+
+.. automodule:: tempest.cmd.javelin