Linking against ATen requires some work

[ezyang]

Using the Conda build of ATen at https://anaconda.org/ezyang/aten it still requires some work to actually link against ATen. In the end, this incant was sufficient for me:

LD_LIBRARY_PATH=$CUDA_HOME/lib64:$CONDA_PREFIX/lib g++ -I$CONDA_PREFIX/include -L$CONDA_PREFIX/lib -lATen -std=c++11 myprog.cpp

(though I don't claim that this is the "best" way to do it.)

We should either document this or make it easier.