Mock out the underlying segment-io call.

TE-532
Fix another analytics.init secret error message (noise).
Pipe analytics client output to stdout instead of devnull.
Add header row to email opt in list; add default date
fix preview link generation for course reruns (PLAT-336)
Merge pull request #6233 from edx/adam/fix-preview-courseruns

fix preview link generation for course reruns (PLAT-336)
Merge pull request #6245 from edx/will/email-opt-in-updates

Add header row to email opt in list; add default date
Separate verification / payment flow.
Merge pull request #6247 from edx/will/update-verified-requirements

Separate verification / payment flow.
Merge pull request #6240 from edx/benp/fix-analytics-init

Mock out the underlying segment-io call.
WL-172 Show a Order History list on the Student Dashboard for any PaidCourseRegistration or RegCodeItem that the user might have purchased