Change output_declarations in function_wrapper.py to be a NamedTuple (pytorch#5312)

* Add python typing module as build dependency

* Change output_declarations to be a NamedTuple

* Add mypy configuration files

mypy-files.txt includes a list of all files that should be typed checked
with mypy. Run mypy with `mypy @mypyfiles.txt`.

mypy.ini includes mypy options. Unfortunately this can't be merged with
mypy-files.txt.

Update .travis.yml so that one doesn't have to specify what files to
type check inside it.

* Add RuntimeError on missing `typing` module

Alerts users to the new build dependency.

Author: zou3519

.travis.yml

@@ -16,8 +16,7 @@ matrix:
         python: "2.7"
         install: pip install flake8
         script: flake8
-      # mypy will complain about various files. Limiting it to only typed files
       - env: MYPY_TYPE_CHECK
         python: "3.6"
         install: pip install mypy mypy-extensions
-        script: mypy --py2 aten/src/ATen/function_wrapper.py
+        script: mypy @mypy-files.txt

README.md

@@ -171,7 +171,7 @@ On Linux
 export CMAKE_PREFIX_PATH="$(dirname $(which conda))/../" # [anaconda root directory]
 
 # Install basic dependencies
-conda install numpy pyyaml mkl setuptools cmake cffi
+conda install numpy pyyaml mkl setuptools cmake cffi typing
 
 # Add LAPACK support for the GPU
 conda install -c pytorch magma-cuda80 # or magma-cuda90 if CUDA 9