removed commented test_remote_data
added new calculation

A custom computations was added for the QED workshop. This required
some new customizations for the calculation engine. All tests are
working and the code should not be too insidious. Also added the
time region print out to the metadata file.
added freq_duration example for testing
fixed bug with index in frequency duration.
modifications to frequency duration test
testing dynamic percentiles
hotfix for path to csvs
fixed bug with format_return where the file was always unzipped as 'shp'
regardless of contents.
minor changes to shp_scanner to modify the US county name
i-178: snowfall water equivalent computations

Support for snowfall water equivalent index computations. There
were changes to the request dataset object and naming of the
abstraction parameter. Returning datetime objects from the dataset
directly now requires calling a specific property.
Merge branch 'i-178-sfwe' into dev

Conflicts:
	src/ocgis/calc/base.py
	src/ocgis/calc/engine.py
	src/ocgis/test/test_calc.py
	src/ocgis/test/test_qed.py
	src/ocgis/test/test_remote_data.py
	src/ocgis/util/environment.py
length of shapefile changed. tests changed to acount for new point
geometry.