new CubeList method to extract over common coord values
Changed to generator comprehension
progress
new metarelate api
review actions
Forecast/observation reference time
doc: Fix short documentation header line.
doc: Add newlines to fix Sphinx warnings.

reST requires newlines between blocks that change indentation. Sphinx
doesn't seem to mind, mostly, but it produces a lot of warnings if
they're missing.
doc: Add missing toctree entries.
Merge pull request #1355 from QuLogic/doc-updates

Documentation updates
rereview
The dead simplest lower the bar, move the bar, trip over the bar, pyugrid/iris integration.
Fix test failures and add trivial test assertion.
Merge pull request #1359 from rhattersley/ugrid

(Highly!) experimental UGRID support
Use new-style exception syntax.
Use new function attribute names.
Use 'in' operator instead of 'has_key' method.
reduce is no longer a global function in Py3.
Fix lambda functions that take tuples.

Python 3 will no longer unpack them into multiple arguments.
Add spaces after commas.