BLD: Added debug to conda

Listing conda packages allows us to determine what changes have occurred
from one travis build to the next in terms of the conda packages
installed.
Merge pull request #477 from cpelley/conda_debug

Run ```conda list``` in travis build to simplify debugging.
Initial work
boundary/edge issues resolved
further mods
Added testing and fallback for multiple projections
pep8
Correct RasterSource.validate_projection docstring
Refactor SRS determination.
Allow multi-image responses
Bug fixes and review feedback.
Add/update tests
Merge pull request #1 from rhattersley/wms_diff

Update WMS handling
Update heuristics and test result.
Merge pull request #2 from rhattersley/wms_diff

Update heuristics and test result.
Merge pull request #507 from esc24/wms_diff

Ability to add WMS layers to different GeoAxes projections
Nearly-working bones of adding WFS to Cartopy
Initial pass
further progress
more changes