Nansat v0.6.7 stable

Stable version of Nansat integrated with nansen-cloud, nersc-vagrant, nersc-metadata, conda-recipes and nansat-lectures.

Main changes:

• mappers add standardized metadata (time_coverage_start, platform, instrument, etc);
• get_transect returns recarray;
• TravisCI uses miniconda;
• export2thredds works fine;
• adds random colorbar for a map;
• read OC CCI, OC SST, GLOB-CURRENT products
  and many more ...