revise to use quandl_logger
revise to use logger in classes
require logger
bump
bump quandl_logger
add valid_collapses to Collapse
improve log info
invalid format returns data
fix collapse bug
cumul requires data to be in desc order
parse does not sort
bump
bump to release
Merge pull request #1 from RaymondMcT/master

Merging new transformation
add Transform rdiff_from
Merge branch 'master' of github.com:quandl/quandl_operation