fixed call to client_authentication_required
added test involving client_authentication_required method
fixed operator precedence in duplicate_params property
added myself to the authors list
broke up method into different tests, fixed import style
fixed and extended tests for validate_token_request method
Merge pull request #214 from masci/fix_client_authentication_required_call

Fix bug in client_authentication_required call
Restructure client tests per grant type.
Accept new unix timestamp param expires_at in tokens.
Populate a unix timestamp expires_at from expires_in in new tokens.
Merge branch 'master' of https://github.com/idan/oauthlib
Set headers on client credentials access token response
Merge pull request #216 from ButchershopCreative/master

Set headers on client credentials access token response
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Fix all application/json mimetypes.
Merge pull request #217 from lepture/fix-json

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