pullrequest testing

**tests** directory contains tests and pytest local plugin (**tests/testrunner/conftest.py**) to run all of them.
**ansible** directory contains ansible playbooks (ans some others files) to prepare test environment and run tests.
**lib** directory contains python modules for tests and the plugin.

When pull-request-test is finished there will be a message about that on pull request page:
"All is well — Finished TeamCity Build Elliptics Сocaine Tests :: Pull Request Testing : Tests passed: 4"
You can see an example here: https://github.com/kis8P-team/elliptics/pull/6

@uvizhe, take a look at this review