[#36112169]add mandrill to gemfile
[#36112169]configure mandrill smtp
[#36112169]add send_weekly_reports boolean to business config
[#36112169]setup mandrill_mailer
[#36112169]add httparty to gemfile, for use when communicating with the highcharts api
[#36112169]use forked version of mandrill_mailer that has images option
[#36112169]weekly stats mailer sends debit and credit piecharts
[#36112169]weekly stats mailer lists memberships
[#36112169]paid/unpaid installments on mailer
[#36112169]sales and enrollments on mail
[#36112169]rake task for weekly stats
Merge 36112169-weekly-report to master

[Completes #36112169]