[RENAME] nvcc_compiler->nvcc, cc_compiler->cc, metal_compiler->xcode (#248)

docs/api/python/contrib.rst

python/tvm/contrib/cc.py

python/tvm/contrib/nvcc.py

python/tvm/contrib/rpc.py

python/tvm/contrib/xcode.py

python/tvm/module.py

src/common/socket.h

tests/python/unittest/test_codegen_cross_llvm.py

tests/python/unittest/test_module_load.py

tests/scripts/task_python_docs.sh

tests/scripts/task_python_integration.sh

tests/scripts/task_python_unittest.sh

topi/recipe/conv/depthwise_conv2d_map_test.py

topi/recipe/gemm/cuda_gemm_square.py

topi/recipe/rnn/lstm.py

topi/recipe/rnn/matexp.py

tutorials/python/get_started.py