Sepiida

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Update cryptography dependency to the latest for Ubuntu 16.04 support

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Add sepiida.wsgi.stabilize_werkzeug_iterator(). This function should be called first in wsgihandler modules that use
flask to prevent us from getting unhandled exceptions on clients that disonnect before we finish sending the response. This common in bots.

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This extends sepiida.FilterArgument to work with ISO8601 dates. e.g. filter[created]=2015-01-01
https://some.service/?filter[id]=1,2&filter[id]=3
will result:

self.filters = {
'id' : [
FilterArgument(name='id', operation='=', values=[1,2]),
FilterArgument(name='id', operation='=', values=[3]),
]
}

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This introduces a new way for sepiida to handle content types and serialization. We are no longer only doing JSON, but instead support JSON and
form-encoded URL data. We do this via content negotiation, so this introduces new error modes for inability to negotiate a type.

In support of this the JSONObject and JSONArray classes are renamed to just Object and Array, respectively. Errors that specifically mentioned
JSON in some places have been updated to only mention JSON if we are encoding to JSON.

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Fix sepiida.groups.has_any to work with group names, not with group uris