Adds diagrams for the high availability page (#96)

Author: sarahsimpers

source/high-availability.txt

@@ -58,6 +58,11 @@ Recommended Deployment Topologies
 
 Single Region, 3 Node Replica Set / Shard (Primary Secondary Secondary)
 ```````````````````````````````````````````````````````````````````````
+
+.. figure:: /includes/images/highavailabilityPSS.svg
+   :figwidth: 750px
+   :alt: A topology with a single region with 3 nodes: one primary and two secondaries.
+
 This topology is appropriate if low latency is required but high availability requirements 
 are limited to a single region. This topology can tolerate any 1 node failure and easily satisfy majority write 
 concern within region secondaries. This will maintain a primary in the preferred region upon any node 
@@ -68,6 +73,11 @@ This topology, however, can't tolerate a regional outage.
 
 3-Region, 3 Node Replica Set / Shard (Primary - Secondary - Secondary)
 ``````````````````````````````````````````````````````````````````````
+
+.. figure:: /includes/images/highavailabilityP-S-S.svg
+   :figwidth: 750px
+   :alt: A topology with a three regions. There is one primary node in the first region, one secondary node in the second region, and one secondary node in the third region.
+
 This topology is the standard multi-regional topology where high availability can be provided to tolerate a regional outage. 
 This topology can tolerate any 1 node failure, any 1 region outage, and is the least expensive multi-region topology. 
 
@@ -79,6 +89,11 @@ application architecture must adjust as a result.
 
 3-Region, 5 Node Replica Set / Shard (Primary Secondary - Secondary Secondary - Secondary)
 ``````````````````````````````````````````````````````````````````````````````````````````
+
+.. figure:: /includes/images/highavailabilityPS-SS-S.svg
+   :figwidth: 750px
+   :alt: A topology with a three regions. There is one primary node and one secondary node in the first region, two secondary nodes in the second region, and one secondary node in the third region.
+
 This topology is the preferred topology that balances high availability, performance, and cost across multiple regions. 
 This topology can tolerate any 2 nodes' failure, tolerate primary node failure 
 while keeping the new primary in the preferred region, and tolerate any 1 region outage.