Updated INSTALL and iris.config documentation and added an example site.cfg.template
travis (nodata)
github/travis playbad repush
Merge pull request #304 from bblay/travis_nodata

travis-ci support for the no-data tests.
Added an example of rolling_window with weights.
Config doc-string changes.
Merge pull request #309 from ajdawson/soi-example

Added an example of rolling_window with weights.
Merge pull request #315 from bjlittle/document_sitecfg_patch

Document sitecfg patch
Updated the extests to easily support image tolerances.