Opentracing-instrumentation

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- Add client hooks for psycopg2 (39)

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- Futurize to support Python 3
- Add interceptor support to ``opentracing_instrumentation.http_client``
- Add function to install interceptors from list

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- Upgrade to opentracing 1.2 with KV logging

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- Remove url encoding/decoding when using HTTP_HEADERS codecs

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- Match redis.set() signature

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- Fix monkeypatched argument names in redis hooks