hugegraph-81 add github link to README

Change-Id: I16f47975372a5cb88b3890407a6e9d5fd79e19f9
diff --git a/README.md b/README.md
index db855b5..ab64c6d 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 # hugegraph-common
 
-hugegraph-common is a tool module for [HugeGraph]() and its peripheral components.
+hugegraph-common is a tool module for [HugeGraph](https://github.com/hugegraph/hugegraph) and its peripheral components.
 hugegraph-common encapsulates locks, configurations, events, iterators, rest and some 
 numeric or collection util classes to simplify the development of HugeGraph and 
 its components.