CPP-816 - Add quickstart guide for Constellation (#296)

* CPP-816 - Add quickstart guide for Constellation

Author: mikefero

cpp-driver/topics/cloud/README.md

@@ -0,0 +1,50 @@
+# Cloud
+
+## Connecting to your [DataStax Apollo database on Constellation] using a secure connection bundle
+
+   **Note:** Both the C++ Driver for Apache Cassandra and the C++ Driver for DataStax
+   Enterprise (DSE) use the same code to connect and query your Cassandra database,
+   but when using the DSE driver use the header `#include <dse.h>`.
+
+   Use the following code snippet to connect your database:
+
+   ```c
+   #include <cassandra.h> /* Use "#include <dse.h>" when using the C++ DSE Driver */
+   #include <stdio.h>
+
+   int main(int argc, char* argv[]) {
+     /* Setup and connect to cluster */
+     CassCluster* cluster = cass_cluster_new();
+     CassSession* session = cass_session_new();
+
+     /* Setup driver to connect to the cloud using the secure connection bundle */
+     const char* secure_connect_bundle = "/path/to/secure-connect-database_name.zip";
+     if (cass_cluster_set_cloud_secure_connection_bundle(cluster, secure_connect_bundle) != CASS_OK) {
+       fprintf(stderr, "Unable to configure cloud using the secure connection bundle: %s\n",
+               secure_connect_bundle);
+       return 1;
+     }
+
+     /* Set credentials provided when creating your database */
+     cass_cluster_set_credentials(cluster, "username", "password");
+
+     CassFuture* connect_future = cass_session_connect(session, cluster);
+
+     if (cass_future_error_code(connect_future) == CASS_OK) {
+       /* Use the session to run queries */
+     } else {
+       /* Handle error */
+     }
+
+     cass_future_free(connect_future);
+     cass_cluster_free(cluster);
+     cass_session_free(session);
+
+     return 0;
+   }
+   ```
+
+  **Note:** `cass_cluster_set_contact_points()` and `cass_cluster_set_ssl()` should not used
+  in conjunction with `cass_cluster_set_cloud_secure_connection_bundle()`.
+
+[DataStax Apollo database on Constellation]: https://constellation.datastax.com/