added BitbucketPullrequestPoller changes source

The BitbucketPullrequestPoller polls a Bitbucket repository (merucrial
or git) for new or updated pull requests.

* master/buildbot/changes/bitbucket.py: added
added BitbucketPullrequestPoller documentation

* master/docs/manual/cfg-changesources.rst: added documentation
* master/docs/relnotes/index.rst: added release note
fix BitbucketPullrequestPoller issues
added BitbucketPullrequestPoller tests
BitbucketPullrequestPoller unittests fixed pep8 issues
BitbucketPullrequestPoller removed log messages
Support tagging instances after they have launched.
add some unit tests for EC2LatentBuildSlave
make botoSetup return connection
don't call create_tags unecessarily
test start_instance with tags
document tags parameter for EC2LatentBuildSlave
skip ec2 buildslave tests if moto not found
remove moto dependency from setup.py
skip ec2 buildslave tests if moto version is not up to date
add lost comma to setup.py
Merge zapster/buildbot:bitbucket-pullrequest-fix (PR #1064)

Conflicts:
	master/docs/relnotes/index.rst

+autopep8
fix py25 compat: strptime doesn't support %f
Merge longaccess/buildbot:tags (PR #1067)
Actually skip tests when boto's not installed

+autopep8