Add initializers to dynet_viz
Add initializers to dynet_viz

Otherwise using --dynet-viz results in an error if there is e.g.
GlorotInitializer in the graph.


Former-commit-id: fbfe34f94a9a210c55d5928ed59d8a793e675f85
clab/dynet,xunzhang/dynet,xunzhang/dynet,shuheik/dynet,clab/cnn,clab/cnn,danielhers/dynet,clab/dynet,clab/dynet,shuheik/dynet,clab/dynet,danielhers/dynet,clab/cnn,danielhers/dynet,chunyang-wen/dynet,danielhers/dynet,clab/dynet,xunzhang/dynet,danielhers/dynet,clab/dynet,shuheik/dynet,shuheik/dynet,chunyang-wen/dynet,shuheik/dynet,shuheik/dynet,shuheik/dynet,danielhers/dynet,clab/dynet,chunyang-wen/dynet,xunzhang/dynet,chunyang-wen/dynet,danielhers/dynet