Opentracing-instrumentation

------------------

- Nothing changed yet.

------------------

- Fix test hanging on waiting for DynamoDB (112) <Aliaksei Urbanski>

------------------

- Add additional tags to SQLAlchemy instrumentation (107) <Wyatt Anderson>

------------------

- Fix db_span function of _dbapi2 to work with bytes (105) <Aliaksei Urbanski>
- Fix handling of missing psycopg2 module (104) <Aliaksei Urbanski>

------------------

- Improve support for Boto 3 and S3 (102) <Aliaksei Urbanski>
- Refactor MySQLdb hook (100) <Aliaksei Urbanski>
- Refactor SQLAlchemy hook (98) <Aliaksei Urbanski>
- Fix span context propagation for Celery (97) <Aliaksei Urbanski>
- Use tox for CI instead of travis's matrix (96) <Asher Foa>
- Remove support for Python 3.4 (95) <Asher Foa>

------------------

- Set deploy username and password <Yuri Shkuro>
- Add deploy section into .travis.yml (94) <Aliaksei Urbanski>
- Fix coveralls/boto3 dependency conflict (93) <Aliaksei Urbanski>