Xmlstats-py

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- Complete overhaul of the way data is returned and represented when using this library. Data is now returned as NamedTuples, rather than as either simple dictionaries/lists or "objectified" data as in previous versions.
- Methods were reimplimented to match the endpoints of the xmlstats API. Each method exposed by the XmlStats class corresponds to a single endpoint provided by the API, and accepts the same arguments and parameters. This means users of this library can essentially refer to the already existing xmlstats API documentation.

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Fixes:

- Fixed http_get bug that prevented including paramaters in the next request after a 429 response code from xlmstats server.

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Fixes:

- Fixed format_result bug that prevented higher level API functions from working.

Testing:

- Added some basic tests, with Travis CI integration

Documentation:

- Added Travis CI embedded status image to READMEg

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Fixes:

- Fixed bugs in http_get handling of 429 response from xmlstats API server. http_get now waits for the amount of time specified by server 429 response before continuing to make requests.