Hydrofunctions

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* Added draw_map function for help selecting sites (mcr)
* Added ability to query sites by a bounding box (jdh)
* Revised pandas dataframe column names to be the name composed of the provider, site id, parameter, and statistic (for example. USGS:01638500:00060:0001). (jdh)
* Added qualifiers for each station as a column in the dataframe. (jdh)
* Added ability extract NWIS property data from the response object (for example, siteName). (jdh)

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* Updated to support Python 3.6
* Updated docs, added notebooks (mcr jdh)
* Added parameterCd to allow requests for different datasets (thanks jdhughes-usgs!)
* Added ability to query sites by state or county (jdh)
* Added ability to request lists of sites or counties (jdh)
* Improved column names: now includes site id & variable description (for example, '07228000 - Mean Discharge, cubic feet per second')(jdh)
* Added descriptive warnings to explain why queries fail (mcr)

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* Added tests & documentation.

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* Check user inputs & raise explanatory exceptions
* Extract data from response into a dataframe.
* Stations object for managing data.

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* Set up template for custom exceptions
* Added get_nwis function

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* Customized project boilerplate.