update waterml parsers to handle timeseries returned by WOF GetSites requests
rename key for waterml variables: 'unit' -> 'units'
add tests for wof.core.get_variable_info
add wof.core.get_variable_info()
add network to variable dict only if there actually is a network attribute
minor cleanup for get_values and get_variable_info implementation
normalize parsing of variable time information between different versions of WOF
update WOF tests
move save_pretty_printed_xml function from test_util to util so its easier to import from within ulmo
support getting all variable codes via get_variable_info if variable_code=None
rm wof.pytables (for now)
Merge branch 'wof' of github.com:wilsaj/ulmo into wof

Conflicts:
	ulmo/waterml/common.py