[mongodb] upgraded to latest driver, allow SRV style mongodb URI, fix readme example (#1360)

Author: asya999

README.md

@@ -77,4 +77,4 @@ To build the full distribution, with all database bindings:
 
 To build a single database binding:
 
-    mvn -pl mongodb-binding -am clean package
+    mvn -pl site.ycsb:mongodb-binding -am clean package

mongodb/src/main/java/site/ycsb/db/MongoDbClient.java

@@ -194,10 +194,11 @@ public void init() throws DBException {
 
       url = OptionsSupport.updateUrl(url, props);
 
-      if (!url.startsWith("mongodb://")) {
+      if (!url.startsWith("mongodb://") && !url.startsWith("mongodb+srv://")) {
         System.err.println("ERROR: Invalid URL: '" + url
             + "'. Must be of the form "
-            + "'mongodb://<host1>:<port1>,<host2>:<port2>/database?options'. "
+            + "'mongodb://<host1>:<port1>,<host2>:<port2>/database?options' "
+            + "or 'mongodb+srv://<host>/database?options'. "
             + "http://docs.mongodb.org/manual/reference/connection-string/");
         System.exit(1);
       }

pom.xml

@@ -138,7 +138,7 @@ LICENSE file.
     <kudu.version>1.6.0</kudu.version>
     <maprhbase.version>1.1.8-mapr-1710</maprhbase.version>
     <!--<mapkeeper.version>1.0</mapkeeper.version>-->
-    <mongodb.version>3.8.0</mongodb.version>
+    <mongodb.version>3.11.0</mongodb.version>
     <mongodb.async.version>2.0.1</mongodb.async.version>
     <openjpa.jdbc.version>2.1.1</openjpa.jdbc.version>
     <orientdb.version>2.2.37</orientdb.version>