pycnn: small minibatch usage example
pycnn: small minibatch usage example

Former-commit-id: cda0f971e8c7dcea8f3cccba8b69bf94cffd1fda
danielhers/dynet,shuheik/dynet,shuheik/dynet,shuheik/dynet,shuheik/dynet,chunyang-wen/dynet,clab/dynet,clab/dynet,xunzhang/dynet,danielhers/dynet,clab/cnn,xunzhang/dynet,danielhers/dynet,xunzhang/dynet,danielhers/dynet,shuheik/dynet,chunyang-wen/dynet,danielhers/dynet,clab/dynet,clab/cnn,clab/cnn,danielhers/dynet,danielhers/dynet,shuheik/dynet,shuheik/dynet,clab/dynet,clab/dynet,xunzhang/dynet,chunyang-wen/dynet,clab/dynet,clab/dynet,chunyang-wen/dynet