Adds skip_cleanup option in travis-ci deployment phase to avoid Pypi …

…upload failure:

Deploying application
src/django_dirtyfields.egg-info/PKG-INFO already exists, no checkout
src/django_dirtyfields.egg-info/SOURCES.txt already exists, no checkout
src/django_dirtyfields.egg-info/dependency_links.txt already exists, no checkout
src/django_dirtyfields.egg-info/requires.txt already exists, no checkout
src/django_dirtyfields.egg-info/top_level.txt already exists, no checkout
Could not restore untracked files from stash entry
PyPI upload failed.
failed to deploy

.travis.yml

@@ -59,6 +59,7 @@ after_success:
   - if test "$TOXENV" = "py36-django111-coverage"; then coveralls; fi
 
 deploy:
+  skip_cleanup: true
   provider: pypi
   user: smn
   password: