Andrew Mitrophanov

Test errors caused by Python 2.6: ``` ... File "/home/travis/virtualenv/python2.6.9/lib/python2.6/site-packages/coverage/misc.py", line 287, in class StopEverything(unittest.SkipTest): AttributeError: 'module' object has no attribute 'SkipTest' ```

Let me suggest use [aiofiles](https://github.com/Tinche/aiofiles) and make [Cache](https://github.com/Limych/ha-gismeteo/blob/b2e64881e3c68b03e52bae030f1811c19cf7ad1a/custom_components/gismeteo/cache.py#L15) methods async