Hack in pure-Python PP rules
Add GRIB support and fix remaining issues/tests.
Remove obsolete methods
Delete temp_test_output.txt

Fix to #462.
Convert post-item documentation to pre-item #: form
Merge pull request #618 from rhattersley/docstrings

Convert post-item documentation to pre-item #: form
Merge pull request #611 from rhattersley/rulegen

PP/GRIB load rules as a function
lambert grib