Prevent name clash when importing Celery

[Ed McDonagh]

As per Pull request #203 submitted by @asch99.

[Ed McDonagh]

Branch issue646celerynameclash created to test this contribution

[Ed McDonagh]

Added ref #646 to changes, Arnold to contributing authors.

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[Ed McDonagh]

This looks to be fine, I'm going to pull it in. Thanks @asch99

[Ed McDonagh]

Merged in issue646celerynameclash (pull request #211)

Issue646celerynameclash

Fixes #646, supersedes pull request #203 from @asch99

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[Ed McDonagh]

Merged in release-0.8.1b2 (pull request #216)

Release 0.8.1b2

Some fixes, lots of docs. Refs #647, #646, #647, #648, #649, #650, #651, #652, #653, #654, #656

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