* Display documentations of demos on the Docs.

* Rename the title from `demos` to `Examples`.

* Provide English tutorial on how to use VisualDL in Keras

* Add the English Tutorial of PyTorch.

* Add the English MXNet tutorial.

* Remove links in the MXNet tutorial.

* support manylinux build

* mxnet graph

* long graph

* added full graph

* add gif back

* updated gif

* fix comments

* remove python highlight for one line

* demo mxnet

* test refer local file

* to english

* link anchor

* anchor should work

* anchor to lower case

* pylint