Updated description of memory in the README
Updated description of memory in the README


Former-commit-id: f46b39cf1c3ee5e95a112467c3e083cb024a312e
clab/dynet,chunyang-wen/dynet,shuheik/dynet,clab/dynet,danielhers/dynet,danielhers/dynet,shuheik/dynet,chunyang-wen/dynet,shuheik/dynet,xunzhang/dynet,clab/cnn,danielhers/dynet,shuheik/dynet,danielhers/dynet,clab/dynet,danielhers/dynet,clab/dynet,shuheik/dynet,danielhers/dynet,clab/cnn,chunyang-wen/dynet,xunzhang/dynet,shuheik/dynet,clab/cnn,danielhers/dynet,chunyang-wen/dynet,clab/dynet,clab/dynet,clab/dynet,shuheik/dynet,xunzhang/dynet,xunzhang/dynet