Nansat

Changelog
* Update of tests: PointBrowser tests are made qt5 independent; Exporter tests write temporary files;

Change-log:
* Add Nansat.extend()
* DRY netCDF Mapper
* Fix Envisat Mapper to use open() instead of file()
* Fix Geolocation to take VRT objects
* Add Nansatmap and other issues of backwards compatibility
* Improve links for dependencies in docs
* Fix read-the-docs
* Update conventions of merging/branching in the docs
* Remove using old errors from Nansat and other modules

A major revision of Nansat!

* Works on all major platforms: Windows, Linux and OS X
* Works on Python 3.5 and 3.6 as well as 2.7
* Integrated with PyPi
* Installation is made a lot easier with Anaconda
* All documentation is now available at https://nansat.readthedocs.io
* Major refactoring of the code
* Increased test coverage to 90%
* Removed Mosaic and Nansatmap modules to their own repositories
* Bugfixes

Bug fix in mapper for netcdf-cf files

New mappers for netcdf-cf files from AROME and ECMWF weather products. Updated opendap and Sentinel-1 mappers. Plus other small improvements and bug fixes.

Stable version of Nansat
Changelog:
- New OPENDAP mappers to access:
- OC CCI
- SST CCI
- METNO SIWTAC
- METNO OSISAF
- GLOBCURRENT
- All OpenDAP mappers now inherit from mappers/opendap:Opendap. Mappers ..._online are removed;
- Add DataForTestingOnlineMappers and TestOnlineMappers to end2endtests;
- Domain.write_map can add several patches to the map;
- mapper globcolour reads also PAR;
- mapper globcolour_l3b creates TMP file for netDCF4;
- mapper modis_l1 adds at least 30x30 GCPs from lon/lat bands;
- mapper obpg_l2 sets correct platform for SeaWiFS
- Mapper sentinel_1a can read all metadata from manifest and other XML files (also zipped);
- nansat.reproject strictly requires domain
- Unittests for Node are added
- More unittests for Nansat are added
- Unittests for PointBrowser are added