Add gitlab CI config

.gitlab-ci.yml

+image: clarinpl/python:3.6
+
+before_script:
+  - pip install tox==2.9.1
+
+cache:
+  paths:
+  - .tox
+
+stages:
+ - check_style
+ - push_wheel
+
+pep8:
+  stage: check_style
+  script:
+   - tox -v -e pep8
+
+docstyle:
+  stage: check_style
+  script:
+   - tox -v -e docstyle
+
+push_wheel:
+  before_script:
+   - pip install twine
+  only:
+   - master
+  stage: push_wheel
+  when: on_success
+  script:
+   - python setup.py sdist bdist_wheel
+   - python -m twine upload 
+     --repository-url https://pypi.clarin-pl.eu/
+     -u $PIPY_USER -p $PIPY_PASS dist/cclutils*.whl
+
+