minor: default mapper in Nansat; first take band name from metadata name in mapper_generic.py
Merge branch 'develop' of https://github.com/nansencenter/nansat into develop
temporary fix for failing gdal install (Travis CI)

see https://github.com/travis-ci/travis-ci/issues/2683
ref discussion in #87 - moved import of mappers in nansat.py and Nansat in mapper_ncep_wind_online.py to avoid recursive import of Nansat and to make it possible to import Nansat at the top of the mapper modules instead of inside the __init__ methods
updated mapper imports
added skip decorator for some tests of which the test data is proprietary and cannot be shared
removed warnings
#92 remove unwanted matadata in nansat.export2thredds
#92: Change time dimension from int to float in nansat.export2thredds().
#92 add grid_mapping metadata to all bands in nansat.export2thredds().
#92 Get rid of some arguments of nansat.export2thredds().
Fixed bug in vrt.get_resized_vrt(); add shift of half pixel to compensate for pixel-centre vs pixel-edge in geotransform
Merge branch 'issue86-resize-vrt' into develop
for use with python 2.6
#92 Fix a bug of nansat.export2thredds().
Fixed bug in Radarsat2 mapper: SAR look direction was wrong for ascending pass
bug fix in method get_transect
Merge branch 'develop' of https://github.com/nansencenter/nansat into develop
slightly changed method for estimating the look direction and added explanation
#92 dont limit export2thredds to longlat and stere projections