[Doc] fix link in README (#296)

* fix mxnet link

* fix issue link

README.md

@@ -37,7 +37,7 @@ DGL should work on
 
 DGL also requires Python 3.5 or later.  Python 2 support is coming.
 
-Right now, DGL works on [PyTorch](https://pytorch.org) 0.4.1+ and [MXNet](mxnet.apache.org) nightly
+Right now, DGL works on [PyTorch](https://pytorch.org) 0.4.1+ and [MXNet](https://mxnet.apache.org) nightly
 build.
 
 ## Installation
@@ -144,7 +144,7 @@ For more realistic, end-to-end examples, please see [model tutorials](https://do
 
 ## Contributing
 
-Please let us know if you encounter a bug or have any suggestions by [filing an issue](https://github.com/jermainewang/dgl/issues).
+Please let us know if you encounter a bug or have any suggestions by [filing an issue](https://github.com/dmlc/dgl/issues).
 
 We welcome all contributions from bug fixes to new features and extensions.
 We expect all contributions discussed in the issue tracker and going through PRs.  Please refer to the PR guide.