Deform-bootstrap

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- All deformdemo Selenium tests passing.

- Add sequence templates.

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- In ``includeme``, prepend deform search path instead of resetting
the whole renderer.

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- Changes to support Bootstrap 2.0.

- Added support for Bootstrap's feature to prepend/append text to
``input[type=text]`` via input_prepend/input_append keyword
arguments to ``deform.Widget`` constructor.