update sms_billables view for extra information necessary to fix MachBillables bug
adding additional information in emit of sms_billables view
this line in sms_billables is for debugging
fix reports and model to use the most recent billable for a message_log id
management command to set the billable_date on mach billables to the date the message log was sent
fix help text for fix_mach_billables command
also order by modified date in smsbillables in addition to billable_date
cleanup only pull the latest billable by message log for the bill
Merge pull request #36 from dimagi/mach-hotfix

It seems an earlier run of the management command to fix Mach Billables was in error