added tests for GRIB ProductDefinition 4.9 and to fail unrecognised PDTs
tidied new tests and revised for different proposed solution
added partial support for GRIB2 PDT4.9 ; tidied test_grib_load
fix test comment in test_grib_load
grib_rules.txt: tidied string formatting
test_grib_load.py:
  added comments highlightling partial PDT4.9 support
  fix bug in temporary file management : use 'unittest.temp_filename' in preference to 'tempfile'
  use unittest.temp_filename in place of tempfile methods
  various PEP8 fixes for layout + naming
Cache netCDF attributes.
Fieldsfile and PP support for unpacked and CRAY 32-bit packed data.
Merge pull request #210 from bjlittle/unpacked_and_cray32

Fieldsfile and PP support for unpacked and CRAY 32-bit packed data.
Changed data_dim to an argument not keyword
Merge pull request #213 from rhattersley/cf-attr-cache

Cache netCDF attributes
new test file for cube
Deferred loading of AuxCoord points/bounds.
Updated test class. Closes #178
Faster masked array creation in DataManager.
Faster masked array creation in merge
first results
tests (using mock!)
Tweak comment and error text
Merge pull request #218 from rhattersley/fast-mask

Faster masked array creation in DataManager.
replace large COLPEX files with 'stock' data in test_plot