CPP implementation of L2Norm and LRN ops (#1157)

nnvm/include/nnvm/top/nn.h

nnvm/python/nnvm/top/nn.py

nnvm/src/top/nn/nn.cc

nnvm/tests/python/compiler/test_top_level1.py

topi/include/topi/cuda/normalization.h

topi/include/topi/nn/l2_normalize.h

topi/include/topi/nn/local_response_norm.h

topi/include/topi/rocm/normalization.h

topi/python/topi/cuda/__init__.py

topi/python/topi/cuda/nn.py

topi/python/topi/generic/nn.py

topi/python/topi/nn/__init__.py

topi/python/topi/nn/l2_normalize.py

topi/python/topi/nn/local_response_norm.py

topi/python/topi/rocm/nn.py

topi/python/topi/testing/__init__.py

topi/python/topi/testing/l2_normalize_python.py

topi/python/topi/testing/lrn_python.py

topi/src/topi.cc

topi/tests/python/test_topi_l2norm.py