Modify EventLogSelectionTask to accept multiple values for source parameter.

Values in config files are specified on separate lines.  E.g.:

  [event-logs]
  source = s3://fake/input/
           s3://fake/input2/
Breakdown historical enrollment trends by demographic traits
fixup! Breakdown historical enrollment trends by demographic traits
Merge pull request #16 from edx/gabe/demographics-minimal-refactor

Demographics initial work
Update get_filename_safe_course_id to be more restrictive.

Instead of hardcoding knowledge about colons, just replace all
but a well-defined set of supported characters.

And fix a PEP8 violation.
Merge pull request #17 from edx/brian/multiple-event-src

Modify EventLogSelectionTask to accept multiple values for source parameter.
Merge pull request #23 from edx/brian/fix-safe-file

Update get_filename_safe_course_id to be more restrictive.
Add handling for answer strings that convert to float inf and nan
Fix acceptance tests given latest changes to exporter

adding new arg

verifying failure on misconfig

Revert "verifying failure on misconfig"

This reverts commit 0570f31f01138b3390d02667d16bb909d956779b.

updating pipeline bucket arg

cr comments
Merge pull request #27 from edx/jbau/handle-NaN-inf-conversions

Add handling for answer strings that convert to float inf and nan
Merge pull request #26 from edx/gabe/fix-acceptance-tests

Gabe/fix acceptance tests
try hardcoding customresponse