Added pycnn_viz example
Added pycnn_viz example

Former-commit-id: ec75eb85932f964e5c3ad79515b4b2c45c84f9a3
clab/cnn,xunzhang/dynet,clab/dynet,clab/dynet,danielhers/dynet,shuheik/dynet,shuheik/dynet,clab/dynet,xunzhang/dynet,clab/dynet,chunyang-wen/dynet,shuheik/dynet,clab/cnn,danielhers/dynet,xunzhang/dynet,chunyang-wen/dynet,clab/cnn,shuheik/dynet,shuheik/dynet,danielhers/dynet,clab/dynet,danielhers/dynet,danielhers/dynet,chunyang-wen/dynet,shuheik/dynet,chunyang-wen/dynet,shuheik/dynet,clab/dynet,danielhers/dynet,danielhers/dynet,xunzhang/dynet,clab/dynet