[CORD-1795] Document the new TOSCA engine

Change-Id: Ibaf94f9e680ecb780e76d971b5cad26405de106b
diff --git a/.gitignore b/.gitignore
index 900c131..3117408 100644
--- a/.gitignore
+++ b/.gitignore
@@ -10,4 +10,5 @@
 coverage.xml
 
 # hack
-xos
\ No newline at end of file
+xos
+_book