Remove bundled lib-typing (#3337)

This gets rid of code duplication and makes sure mypy works with the released version of `typing`. This doesn't fix any immediate issue, but I saw some comments in the bug tracker saying that we should be able to get rid of `lib-typing` eventually.

There is a minor downside: To run mypy tests locally, you will now have to have a Python 2.7 installed that has `typing` available.

Author: JelleZijlstra

.travis.yml

@@ -15,6 +15,7 @@ python:
 
 install:
   - pip install -r test-requirements.txt
+  - python2 -m pip install --user typing
   - python setup.py install
 
 script:

LICENSE

@@ -27,8 +27,7 @@ DEALINGS IN THE SOFTWARE.
 = = = = =
 
 Portions of mypy are licensed under different licenses.  The files
-under stdlib-samples and lib-typing are licensed under the PSF 2
-License, reproduced below.
+under stdlib-samples are licensed under the PSF 2 License, reproduced below.
 
 = = = = =