removing pthread from tutorial cmakelists. Not being used.
removing pthread from tutorial cmakelists. Not being used.


Former-commit-id: 97f8ccaa06ff50cfc660b3b44c4ae18b2458ee28
clab/dynet,xunzhang/dynet,clab/dynet,clab/dynet,clab/dynet,shuheik/dynet,danielhers/dynet,danielhers/dynet,clab/cnn,xunzhang/dynet,shuheik/dynet,chunyang-wen/dynet,xunzhang/dynet,shuheik/dynet,shuheik/dynet,danielhers/dynet,clab/dynet,shuheik/dynet,clab/dynet,danielhers/dynet,clab/dynet,clab/cnn,xunzhang/dynet,chunyang-wen/dynet,chunyang-wen/dynet,danielhers/dynet,shuheik/dynet,shuheik/dynet,danielhers/dynet,chunyang-wen/dynet,clab/cnn,danielhers/dynet