Ddtrace

Integrations
- [pylons] allow users to set resources inside handlers
- [django] add support for the Django cache framework

Enhancements
- add a trace sampler so that users can discard spans using a `RateSampler` (more info: http://pypi.datadoghq.com/trace/docs/#sampling)

Read the [full changeset](https://github.com/DataDog/dd-trace-py/compare/v0.3.13...v0.3.14)

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New integrations
- added `pylibmc` Memcached client integration
- improved Django integration providing a Django app that instrument Django internals

Read the full [changeset](https://github.com/DataDog/dd-trace-py/compare/v0.3.12...v0.3.13)

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[change set](https://github.com/DataDog/dd-trace-py/compare/v0.3.11...v0.3.12)
- Added MySQL integration, using [mysql.connector](https://dev.mysql.com/doc/connector-python/en/) v2.1

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Bugfixes
- fixed an unpacking error for `elasticsearch>=2.4`
- fixed the behavior of the `tracer.wrap()` method; now it works as expected

Documentation
- better organization of libraries usage on docs
- provided a [benchmark script](https://github.com/DataDog/dd-trace-py/commit/7d30c2d6703e21ea3dc94ecdeb88dbe2ad9a286a)

Read the [full changeset](https://github.com/DataDog/dd-trace-py/compare/v0.3.10...v0.3.11)

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[change set](https://github.com/DataDog/dd-trace-py/compare/v0.3.9...v0.3.10)
- add `flask_cache` integration; supporting the `0.12` and `0.13` versions
- catch `500` errors on `pylons` integration

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[change set](https://github.com/DataDog/dd-trace-py/compare/v0.3.8...v0.3.9)
- send service info from the sqlalchemy integration

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