chore: Bump version to 0.2.0b1

Version 0.2.0a1

Version 0.1.8

Falcon version 0.1.8rc3

Falcon version 0.1.8rc2

Falcon version 0.1.8rc1

Release Candidate 1

Version 0.1.7

Version 0.1.6.post3

Version 0.1.6.post2

Fixed
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* testtools is no longer a required dependency (cabrera)

New
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* Add HTTPNotAcceptable for responding with HTTP status code 406 (lichray)
* Add HTTPLenghRequired for responding with HTTP status code 411 (cabrera)
* Add generic req.client_accepts() method (lichray)