Make sure *.pyc files are not included in the tarball

[mitya57]

The current tarball on PyPI contains unwanted files:

• test/.DS_Store
• test/__pycache__/__init__.cpython-36.pyc
• test/__pycache__/test_get.cpython-36.pyc

This pull request modifies MANIFEST.in to make sure only *.py and test images are included under test/.

How to test: run python3 setup.py test sdist, the output should be like following:

running sdist
...
copying test/__init__.py -> imagesize-1.1.0/test
copying test/test_get.py -> imagesize-1.1.0/test
copying test/images/multipage_tiff_example.tif -> imagesize-1.1.0/test/images
copying test/images/test.gif -> imagesize-1.1.0/test/images
copying test/images/test.jp2 -> imagesize-1.1.0/test/images
copying test/images/test.jpg -> imagesize-1.1.0/test/images
copying test/images/test.png -> imagesize-1.1.0/test/images
copying test/images/test.tiff -> imagesize-1.1.0/test/images

And there should be no other files under test/.

[mitya57]

The Python 3.7 tests are failing on Travis because you need to specify dist: xenial and sudo: required for 3.7 only. See for example what I did in mitya57/secretstorage@ec8ab9dd2bc9d81d. If you want, I can include this change in this pull request or in a separate one.

[jdufresne]

The Python 3.7 test failure is fixed by #22.