[#44086353]Add Liquid gem
[#44086353]Add Data attribute to ScheduledMail
[#44086353]create scheduled_mail with encoded data
[#44086353]parse template content with liquid, begin work on ContactDrop with support for Kshêma email variables
[#44086353]Test liquid variables using Drops
[#44086353]use alias_method to support kshêma variables
[#44086353],
[#44086353]time slot, user & trial lesson drop
[#44086353]fix spec
[#44086353]use correct method: PadmaUser.username
Merge 44086353-liquid-templates to master

[#44086353]