Add study_id as an optional field
Fix tests, allow study_id as optional column

Fixes #346
Fix test in util to use qiita config

previously, it assumed the upload dir was /tmp, but this is a setting in
the qiita config file, so it should be honored
Merge pull request #348 from adamrp/study_id_command_line

Study id command line
Merge pull request #350 from adamrp/fix_util_test

Fix test in util to use qiita config