Custom content negotiation

[multimeric]

trafficstars

• Allow an API to define a dictionary of converter functions for different content types, that are run before and after the JSON API schema sees the data. For example:

  api = Api(blueprint=bp, response_renderers={
      'text/csv': render_csv
  }, request_parsers={
      'text/csv': parse_csv
  })
  

• Two tests added in a separate file
• Fixes #170 and/or fixes #13

[coveralls]

Coverage decreased (-2.3%) to 88.518% when pulling 5a7938cafe18c738a81340f939a76c1caad43b41 on TMiguelT:content-negotiation into b44bc08b11213d49fadae873650d3555889052ec on miLibris:master.