Facebook-utils

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- undid some aggressive 2to3 conversions
- integrating ratelimit detection and errors
- last_response_usage is a property now

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- now testing facebook api versions 2.7 - 3.2
- renamed `last_response_ratelimited` to `last_response_usage`; now checking two fields
- marked `last_response_ratelimited` for deprecation
- added `last_response_is_ratelimited`
- tested/works under python3
- added todo

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- catching another form of expired auth access

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- storing the api version internally
- doing some regex checking to ensure a valid api version is sent to the constructor
- reorganized tests to run against multiple API endpoint versions
- adding `fields` argument to:
* graph__url_me_for_access_token (passthrough to `graph__get_profile_for_access_token`)
* graph__url_user_for_access_token (passthrough to `graph__get_profile_for_access_token`)
* oauth_code__get_access_token_and_profile (passthrough to `graph__get_profile_for_access_token`)
* graph__get_profile_for_access_token
- restructured some url templates to use a `qs` querystring instead of attribute names

The reason for the above changes: the `v2.3` deprecation changed some Facebook API behaviors in undocumented ways. Most notably, `email` is not automatically returned with a profile. It must be queried specifically.

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- added 'secure_only' constructor, default True, to ensure https requests
- fixed how pyramid support used 'ssl_verify'
- made url optional to api_proxy, defaulting to the graph url otherwise
- appsecret_proof upgrades for get_data too

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- updates to work with recent facebook api changes
- - some apis now hit different endpoints
- - some response formats have now changed; the minimum 2.3 now uses a json payload instead of urlencoded
- will now look to environment for default api version (`export FBUTILS_FB_API_VERSION=v2.8`)
- will now look to environment for debug (`export FBUTILS_DEBUG=True`)
- fixed typo/rename `fb_grap_api_version` > `fb_api_version`
- redid how urls are generated for clarity
- updated tests
- made interactive tests public
- pyramid integration namespace change -- now `fbutils.`. this is to ensure things break and people upgrade correctly
- set a custom prefix for pyramid paster integration via `fbutils.prefix`
- now supports appsecret_proof
- the url/payload will be inspected for app_secret; if present and the appsecret_proof is required, will augment the requests as needed. this allows for paginated urls from API results to be automatically followed

"""
https://developers.facebook.com/docs/apps/changelog
[Oauth Access Token] Format - The response format of https://www.facebook.com/v2.3/oauth/access_token returned when you exchange a code for an access_token now return valid JSON instead of being URL encoded. The new format of this response is {"access_token": {TOKEN}, "token_type":{TYPE}, "expires_in":{TIME}}. We made this update to be compliant with section 5.1 of RFC 6749.
"""