QUGC-104 Quandl::Client::Dataset #valid? will check #data.valid? and append errors to its own errors.
Merge branch 'master' into develop
Dataset#data= will accept Quandl::Data
quandl data consumes itself
sort_descending on init
bump quandl_data to new minor patch for validation fixes
add version file
Merge branch 'develop'
Version bump to 2.6.0
Updated changelog with commits from 2.6.0
update docs