Reason: allow 'reason' to be overriden in Schedulers and show in Builder page
Reason: update docs and release notes
Add cancelling of all pending builds
Add Travis configuration file
Install pylint, pyflakes and sphinx
Install txgithub on Travis
On Python 2.5 use Twisted and zope.interface versions that works with Python 2.5

pip and easy_install currently can't select latest package version still
supported on current platform.
Disable pylint in Travis

Latest version doesn't work on Python 2.5 and currently Buildbot
doesn't pass pylint tests.
Install txgithub on Travis after Buildbot

Otherwise txgithub installs latest version of Twisted which doesn't work
on Python 2.5.
Disable txgithub on Travis

txgithub requires Twisted >= 12.3.0, which doesn't work on Python 2.5.
Changes to P4 source step

* Ability to not automatically have a `...` suffix to each client-spec
line
* Ability to specify different client spec options
* Ability to specify custom arguments to the `sync` command line
* Fixed some bugs where the `p4base` was used directly in command lines
even though it could be `None` if a custom client spec was specified.
* Fixed a bug where the `timeout` option given to the `P4` step wasn't
passed on to the `RemoteShellCommand`.
* Added unit tests
* Updated documentation
Fixed pyflakes error
Updated release notes
fix build status incompatibility with hpcloud
add testing for status incompatibility with hpcloud
On Python 2.5 use Jinja2 version that works with Python 2.5

Python 2.5 support was dropped in 2.7 release:
<http://jinja.pocoo.org/docs/changelog/#version-2-7>
Add comment about mock on Travis
Install buildbot in first order to force installation of suitable versions for Python 2.5
Don't build documentation on Python 2.5
Install txgithub on Travis on Python > 2.5