feat(enc): test with unicode tmpdir

Borrowed from gitpython-developers/GitPython#543

Author: ankostis

.travis.yml

@@ -8,7 +8,11 @@ python:
   - 3.3
   - 3.4
   - 3.5
+env:
+  # test with paths containing the unicode characters
+  - TMPDIR="/tmp/καλημέρα"
 install:
+  - ln -s /tmp "$TMPDIR"
   - pip install coveralls
 script:
   - ulimit -n 48