Fix punctuation in traversal function documentation

Updated the traversal function documentation to maintain consistency in punctuation.

PR-URL: #617
Credit: @shaymolcho
Close: #617
Reviewed-by: @

Author: shaymolcho

README.md

@@ -371,7 +371,7 @@ again.
 
 ### `g.stream()`
 
-Stream results asynchronously,
+Stream results asynchronously.
 
 ### `g.streamSync()`